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Many companies are locked in a death struggle with spam. Unfortunately, a simple error in your e-mail setup can allow spam to flood your inbox almost unchallenged.
I found this out the hard way, although the solution quickly became obvious. Fortunately, it’s something that almost every company can easily fix, in case the problem is affecting you.
If you have your own Internet domain name, or your company runs an e-mail server, this applies to you. If not, you probably know someone who could use the information below.
It’s common for companies to post a record for a second server as well. This server is said to have a secondary MX record. If the primary mail server is down or too busy to accept messages, the secondary server will be contacted instead by machines trying to send mail. The secondary server will accept the messages and eventually route them to the primary server when it’s once again available. (For technical details, see this Sendmail tutorial.)
Now that you know the basics, you’ll be able to see how spam can pour in if all of this isn’t properly set up.
Opening the Back Door to Spam
Laying out a plan to test antispam appliances, a developer who works in my company decided to assign each device, one at a time, to a second IP address. We duly changed our primary MX record to that second address: 67.40.30.51. (Let’s call this 51.) Within a few days, every mail server on the Internet had cleared the old number out of its cache and was sending our e-mail to the new number.
At this point, any antispam appliance being tested on our 51 address would do its thing, quarantining messages judged to be spam. It would then route the remaining good mail to our real mail server on the 50 address. So far, so good.
The spammers were working the angles like this:
• Primary mail server. Spammers were sending messages to numerous different e-mail addresses, most of them nonexistent, via our primary MX record. Since the primary MX record was now an antispam appliance we were testing, this spam was mostly detected by the appliance and blocked.
• Secondary mail server. Since the spam hadn’t been delivered to the primary MX record, spam servers simply looked up our secondary MX record and delivered the messages there. The real mail server at 50 readily accepted the messages, since the antispam appliance at 51 had been circumvented.
• Old subdomain names. As a result, we quickly deleted 50 as a secondary MX record. Mail servers should then try to send mail only to our primary MX record at 51, where our antispam appliance operates. But many spam servers simply clung to the fully qualified name of our mail server, Northwind. The spam servers continued sending spam directly to the machine at that subdomain name — ignoring the Internet mail protocol, which establishes the MX record as the standard.
A Fast Fix to a Frustrating Problem
Prior to our latest device tests, our mail server had been defended by no antispam appliance. We had configured it to avoid most spam by rejecting any mail sent to nonexistent addresses. It had also been told to automatically drop connections from known spam servers found on Spamhaus.org’s SBL+XBL block list. This reduced the spam we received to manageable levels.
Now that our mail server was on a separate IP address from whatever antispam appliance was currently being tested, however, stronger measures were needed. If your company has a secondary MX record pointing to a backup mail server, you may need to take the following steps, just as we did:
• Delete the secondary MX record. It’s usually not necessary for smaller companies to post a secondary MX record these days, with a mail server that’s at all reliable. Servers that send Internet mail will generally re-try a down server for up to 72 hours before giving up. Unless your mail server conks out for days at a time, these re-tries should be sufficient for you not to miss any mail, even if you have brief outages.
• Protect your secondaries. If your company truly does have redundant mail servers, go ahead and post secondary MX records for them. Any secondary machine, though, must have antispam protection that’s just as strong as the primary machine’s.
• Block inbound mail except from your filter. We configured our firewall to accept e-mail connections only from the antispam appliance at 51. Doing this clobbered the spam servers that were “remembering” our mail server’s IP address and subdomain name (after its secondary MX record was deleted). Good mail servers observed the standard Internet protocol and sent mail through the primary MX record. Spam servers, which don’t follow the rules, couldn’t get in through the back door.
Conclusion
With all of the obscure conventions and jargon of the Internet mail system, it’s not surprising that mail servers can get set up wrong. If that’s the case in your company, spammers are happy to drive right through the hole and deliver plenty of junk to your inboxes.
(For more on protecting your mail server, see my Jan. 24 column.)
An Executive Tech update on “Fixing Elections”
I wrote on Dec. 20, 2005, that two Florida counties had scrapped Diebold-brand electronic vote-counting equipment after computer experts found that results could be changed without detection. I noted later in that article, “Diebold memory cards became an issue in Ohio after the 2004 Presidential election. Secretary of State Kenneth Blackwell ordered the cards and other election records sealed from public inspection until after the state’s electors were sworn in.”
On Dec. 21, Carlo LoParo, a spokesman for the Ohio Secretary of State, e-mailed me, saying, “Diebold electronic voting machines were NOT in use in Ohio during the 2004 election. Further, the story you referenced relates to Ohio law requiring ballots be sealed for a period of 11-15 days after an election to allow for the arrival of overseas absentee ballots. (Please see Ohio Revised Code 3505.32.) This process does not relate to ‘electors’ or the Electoral College.”
I respectfully disagree with these statements.
• The Dayton Daily News and other news outlets reported on Dec. 12, 2004, that election records had been sealed by the Ohio Secretary of State. This was 40 days after the Presidential election, long after the normal 11-to-15-day period. The Daily News reporter wrote: “This period usually lasts about 10 days after the election, but was being extended because an official recount is under way in the state, according to Blackwell spokesman Carlo LoParo.” The final determination of contests for Presidential electors was on Dec. 7, 2004, based on federal law, and Presidential electors voted in each state on Dec. 13, 2004.
Bob Fitrakis, an Ohio attorney who formerly was involved in litigation with the Secretary of State, said in an interview regarding Diebold election services, “GEMS, which is Diebold software, was used to count votes on equipment in about half the counties.” Fitrakis edits the Columbus Free Press.
I would also like to acknowledge the research assistance provided by Mark Crispin Miller, the author of Fooled Again, an October 2005 book that criticizes election practices observed in Ohio and other U.S. states in the 2004 elections.
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Edison Mail App For Mac Review
While there is no dearth of mail apps at the Mac App Store, very few of them are smart enough to keep the ever-loading inbox uncluttered and offer a better way to manage multiple accounts without having to hop from one end to the other. Most feature-packed email apps warrant a steep learning curve, while the minimalist ones lack the tools to meet pro demand. This is why finding the right balance is key for a simplified email management experience. I guess Edison Mail app does the job perfectly.
Edison Mail App for Mac Review: Speed Up Email Management For Desired ProductivityEdison mail app for Mac seeks to become an all-in-one platform for seamless email management. Featuring an intuitive user-interface coupled with AI-powered search, the app seems fully equipped. But then again, there is a big difference between showing plenty of promise and living up to the expectation. So, let’s take a close look at the mail app to figure how well it’s stacked up!
Feature-Rich Yet Pretty Simple to UseThough I always like to have an app with top-of-the-line features at the disposal, I hate to deal with a clunky interface that often demands a steep learning curve. Even after getting a good hang of the features, a clunky interface tends to hinder productivity. That’s the reason why a clean and intuitive UI is the first thing that I make sure to look for in an app.
Probably the best part about Edison is that it doesn’t look daunting despite being feature-rich. The interface sports clean look for smooth-sailing navigation. Being pretty snappier, Edison seldom gets stuck in an ever-loading loop, unlike many other counterparts. Moreover, the presence of an AI-powered search for tracking down a specific email and the intelligent personal assistant makes email management quite straightforward.
Thanks to the personal assistant, you can keep your travel, entertainment, and purchases organized. Not to mention, it also makes a tad easier to track packages, bills, and receipts.
Focused Inbox and Today Folder to Keep Clutter At BayAside from the clean interface, Edison sports a focused inbox that shows only relevant emails, rather than allowing all sorts of emails to clutter the entire inbox. Thus, you won’t have to dig through the whole inbox to find important emails. It could save plenty of time and even play a crucial role in boosting your productivity.
Another feature that’s worth noting is Today Folder that shows up in the left-hand sidebar of the email window. What makes it so handy is the ability to let you check out all the messages that have arrived on a specific day. So, you can use this smart folder to easily keep an eye on the latest messages. And that too right from one spot.
Block Annoying Senders And Disable Read ReceiptsOne of the better ways you can keep noise away from your inbox is by blocking senders that keep bombarding too many irrelevant emails. To ensure annoying senders stay away from your focused inbox, Edison offers a pretty straightforward way of blocking senders. As someone who prefers to keep the unified inbox tidy, I’ve found it quite appreciable.
Though “read-receipts” is a very helpful feature, not everyone may find it worthwhile. Especially those who prefer to have privacy about when they open an email. If you are one of them, chances are you will adore this email app for offering the option to disable read-receipts aka the double-edged sword.
Fully CustomizableFor a personalized experience, customization has a major role to play. And I must say that Edison has looked up to the task on this front.
Based on your taste or for that matter what works best for you, you can customize this email client for macOS to take control of your unified inbox and even fine-tune the interface in line with your workflow.
Beyond customization, Edison features some quick swipe actions so that you can carry out your tasks without having to take the roundabout ways. With an ever-growing library of templates at the disposal, finding the one that can get along nicely with a subject remains plain sailing. Not just that, the app also offers a quick way to mute notifications, ensuring unwanted alerts stay away.
But guess what, the feature that has caught my eyes in Edison Mail App for Mac is the beloved Dark Mode. Yeah, you read that right! The beautiful dark theme not only turns the entire interface pleasing to the eyes but also safeguards the eyes from straining. Save this cool feature for the times when you wish to browse through emails with complete peace of mind.
Integrated With All The Major Email ServicesBuilt for accelerating email management and enhancing productivity, Edison offers seamless integration with all the major email services including Gmail, IMAP, iCloud, Yahoo! Mail, Outlook, Comcast, AOL, and AT&T. So, it doesn’t matter whether you are using Yahoo! Mail, Gmail, or Outlook, you can use this email app for macOS to manage multiple accounts comfortably thanks to a clutter-free universal inbox.
A Couple of DownsidesAs for the shortcomings, there are a couple of features that I find missing. First and foremost, the app doesn’t offer a way to turn off threading. And second, when an email is marked as unread, it marks the entire thread as unread. While these are not deal-breakers for me, I would want them to be sorted out sooner than later.
The good news is that the company has confirmed that they are already working to sort out these shortcomings. So, there is no need to worry about them.
Price And AvailabilityEdison supports OS X 10.10 or later (64-bit processor). As for the price, it’s available for free.
Download
VerdictThe app for mobile devices (iOS and Android) has long been one of my top picks due largely to an aesthetic interface and a smart unified inbox. So, I felt glad when the company introduced a full-fledged desktop app for Mac in December last year.
Even though Edison for macOS is still relatively new, it can safely stake the claim of being the best email app for Mac – by some distance. Whether it’s the intuitive and snappier interface, integration with several email services, or cool swipe actions, the app has ticked off most boxes. And that too without sacrificing speed and productivity – the two key aspects.
What’s your take on Edison? Share your thoughts about this mail app and whether or not you would like to give it a shot on your Mac.
More Reviews For Mac
Author Profile
Jignesh
Jignesh Padhiyar is the co-founder of chúng tôi who has a keen eye for news, rumors, and all the unusual stuff around Apple products. During his tight schedule, Jignesh finds some moments of respite to share side-splitting content on social media.
Difference Between Primary Cell And Secondary Cell
Primary cell
Secondary cell
Read through this article to find out more about primary cells and secondary cells and how these two types of cells are different from each other.
What is a Primary Cell?The type of electric cell which produces electrical energy by the action of an irreversible chemical reaction is called a primary cell. Since the primary cell involves the irreversible chemical reaction, therefore it cannot be recharged. Thus, the primary cells are designed to use once and then discarded.
The energy density of a primary cell is high; hence it discharges very slowly. The terminal voltage of the primary cell is very less than the EMF of the cell, it is because the internal resistance of a primary cell is very high that causes a high voltage drop within the cell while current drawn from it. Inside a primary cell, there is no fluid, hence it is also termed as dry cell.
What is a Secondary Cell?The electric cell which can converter chemical energy into electrical energy and vice-versa is called secondary cell. The secondary cells involve reversible chemical reactions that means while the discharging of the cell the reaction takes place in the forward direction to produce electrical energy and while charging the reaction happens in reverse direction to stores the electrical energy in the form of chemical energy. Therefore, the secondary cells are designed to use repeatedly by recharging them again and again.
In long term, the cost of secondary cells is less than that of the primary cells. However, their initial cost is more than the primary cells. The energy density of the secondary cell is low; hence it discharges very quickly. Although, the EMF and the terminal voltage of a secondary cell is almost equal, it is because it has very low internal resistance that causes a very low voltage drop within the cell while discharging.
Secondary cells are used in laboratories to perform experiments, digital cameras, trimmers and many other electronic devices.
Difference between Primary Cell and Secondary CellThe following table highlights the major differences between a primary cell and a secondary cell −
Basis of Difference Primary Cell Secondary Cell
Definition The type of cell that can only convert the chemical energy into electrical energy is known as primary cell. The type of cell that can convert chemical energy into electrical energy and vice-versa is called secondary cell.
Chemical reaction Primary cell involves irreversible chemical reaction. The reversible chemical reaction takes place in a secondary cell.
Recharging Primary cell cannot be recharged, once it discharged completely. Secondary cell can be recharged many times.
Use Primary cell can be used only once and then discarded. Secondary cell can be used again and again.
Internal resistance The internal resistance of the primary cells is high. Secondary cells have low internal resistance.
Internal voltage drop Primary cells have high internal voltage drop. Secondary cells have low internal voltage drop.
Terminal voltage For a primary cell, the terminal voltage is quite less than the EMF of the cell. The terminal voltage and EMF of a secondary cell are almost equal.
Energy density Primary cells have high energy density. The energy density of a secondary cell is low.
Discharging rate Primary cells discharge slowly. Secondary cells discharge quickly.
Current Primary cells are capable for producing weak currents only. Secondary cells can produce low as well as high currents.
Size and weight The primary cells are smaller in size and light in weight. Secondary cells are comparatively larger in size and heavy.
Inside content There is no fluid inside a primary cell, hence it is sometimes called dry cell. Secondary cell contains wet cell and molten salts inside it.
Initial cost The initial cost of primary cells is low. The initial cost of a secondary cell is relatively high.
Design The design of primary cell is simple. The design of secondary cell is complex.
Examples Dry cells, mercury cell and Daniel cell are the common examples of primary cells. Nickel-cadmium cell, Nickel-iron cell, Lead-acid cell, etc. are the examples of secondary cells.
Applications The primary cells are generally used in clocks, remote controls, torches and many other small sized portable devices. Secondary cells are used in digital cameras, toys, labs to perform experiments, etc.
ConclusionThe most significant difference between primary cells and secondary cells is that a primary cell cannot be recharged again, whereas a secondary cell can be recharged many times. Both primary and secondary cells are widely used in many portable devices to power them.
How To Get Particular Date Records From Time Stamp In Android Sqlite?
android:layout_width = “match_parent” android:layout_height = “match_parent” tools:context = “.MainActivity” <EditText android:id = “@+id/name” android:layout_width = “match_parent” android:hint = “Enter Name” <EditText android:id = “@+id/salary” android:layout_width = “match_parent” android:inputType = “numberDecimal” android:hint = “Enter Salary” <LinearLayout android:layout_width = “wrap_content” <Button android:id = “@+id/save” android:text = “Save” android:layout_width = “wrap_content” <Button android:id = “@+id/refresh” android:text = “Refresh” android:layout_width = “wrap_content” <Button android:id = “@+id/udate” android:text = “Update” android:layout_width = “wrap_content” <Button android:id = “@+id/Delete” android:text = “DeleteALL” android:layout_width = “wrap_content” <ListView android:id = “@+id/listView” android:layout_width = “match_parent” import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.EditText; import android.widget.ListView; import android.widget.Toast; import java.util.ArrayList; public class MainActivity extends AppCompatActivity { Button save, refresh; EditText name, salary; private ListView listView; @Override protected void onCreate(Bundle readdInstanceState) { super.onCreate(readdInstanceState); setContentView(R.layout.activity_main); final DatabaseHelper helper = new DatabaseHelper(this); final ArrayList array_list = helper.getAllCotacts(); name = findViewById(R.id.name); salary = findViewById(R.id.salary); listView = findViewById(R.id.listView); final ArrayAdapter arrayAdapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_list_item_1, array_list); listView.setAdapter(arrayAdapter); @Override if (helper.delete()) { Toast.makeText(MainActivity.this, “Deleted”, Toast.LENGTH_LONG).show(); } else { Toast.makeText(MainActivity.this, “NOT Deleted”, Toast.LENGTH_LONG).show(); } } }); @Override if (!name.getText().toString().isEmpty() && !salary.getText().toString().isEmpty()) { if (helper.update(name.getText().toString(), salary.getText().toString())) { Toast.makeText(MainActivity.this, “Updated”, Toast.LENGTH_LONG).show(); } else { Toast.makeText(MainActivity.this, “NOT Updated”, Toast.LENGTH_LONG).show(); } } else { name.setError(“Enter NAME”); salary.setError(“Enter Salary”); } } }); @Override array_list.clear(); array_list.addAll(helper.getAllCotacts()); arrayAdapter.notifyDataSetChanged(); listView.invalidateViews(); listView.refreshDrawableState(); } }); @Override if (!name.getText().toString().isEmpty() && !salary.getText().toString().isEmpty()) { if (helper.insert(name.getText().toString(), salary.getText().toString())) { Toast.makeText(MainActivity.this, “Inserted”, Toast.LENGTH_LONG).show(); } else { Toast.makeText(MainActivity.this, “NOT Inserted”, Toast.LENGTH_LONG).show(); } } else { name.setError(“Enter NAME”); salary.setError(“Enter Salary”); } } }); } }
Step 4 − Add the following code to src/ DatabaseHelper.java
package com.example.andy.myapplication; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteException; import android.database.sqlite.SQLiteOpenHelper; import java.io.IOException; import java.util.ArrayList; class DatabaseHelper extends SQLiteOpenHelper { public static final String DATABASE_NAME = "salaryDatabase5"; public static final String CONTACTS_TABLE_NAME = "SalaryDetails"; public DatabaseHelper(Context context) { super(context,DATABASE_NAME,null,1); } @Override public void onCreate(SQLiteDatabase db) { try { db.execSQL( "create table "+ CONTACTS_TABLE_NAME +"(id INTEGER PRIMARY KEY, name text,salary text,datetime default current_timestamp )" ); } catch (SQLiteException e) { try { throw new IOException(e); } catch (IOException e1) { e1.printStackTrace(); } } } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { db.execSQL("DROP TABLE IF EXISTS "+CONTACTS_TABLE_NAME); onCreate(db); } public boolean insert(String s, String s1) { SQLiteDatabase db = this.getWritableDatabase(); ContentValues contentValues = new ContentValues(); contentValues.put("name", s); contentValues.put("salary", s1); db.replace(CONTACTS_TABLE_NAME, null, contentValues); return true; } public ArrayList getAllCotacts() { SQLiteDatabase db = this.getReadableDatabase(); res.moveToFirst(); while(res.isAfterLast() = = false) { array_list.add(res.getString(res.getColumnIndex("fullname"))); res.moveToNext(); } return array_list; } public boolean update(String s, String s1) { SQLiteDatabase db = this.getWritableDatabase(); db.execSQL("UPDATE "+CONTACTS_TABLE_NAME+" SET name = "+"'"+s+"', "+ "salary = "+"'"+s1+"'"); return true; } public boolean delete() { SQLiteDatabase db = this.getWritableDatabase(); db.execSQL("DELETE from "+CONTACTS_TABLE_NAME); return true; }Ios 12 Lets Developers Create Extensions For Reporting Unwanted Texts And Calls As Spam
iOS 10 included a CallKit framework that brought a system-wide way for customers to use specialized apps on their iPhone, like Hiya and TrueCaller, that automatically identify and block nuisance calls before the phone even rings. With iOS 12, Apple started allowing developers to write new types of call-blocking extensions that gather information from the user before deciding whether to report or block the number.
NOTE: Apple introduced the Unwanted Communication feature described in this article at WWDC 2023 in June, and we’ve decided to highlight it ahead of iOS 12’s release this Fall.
When an iPhone with iOS 10 or iOS 11 receives an incoming call, the operating system first consults your Contacts app in an attempt to find a matching phone number. If no match is found, it then compares it to the list of phone numbers in your CallKit apps, like Skype.
If there’s a match, the iOS software then displays the identifying label chosen by the app, like Spam or Telemarketing. If your CallKit app determines that an incoming phone number is actually spam, iOS may choose to block the call automatically. The system is tailored for VoIP apps and identifying possible spammy calls initiated from such apps.
With iOS 12, you can also report unsolicited SMS/MMS messages and unwanted phone calls.
Call identification via a third-party extension in iOS 10
Speculation goes that Apple built these enhanced SMS and call spam reporting features into iOS 12 in order to comply with requests from the Telecom Regulatory Authority of India, which has been pressured Apple relentlessly to approve the government’s anti-spam app.
SMS spam is a major problem in India.
Apple took the hard stance by rejecting the app as it did not want any government agency to have full access to users’ call and SMS logs. By creating a new SMS and call reporting extension in iOS 12, Apple might comply with the request without putting user privacy at risk.
Introducing Unwanted CommunicationiOS 12 introduces a new extension type, dubbed Unwanted Communication.
According to the official developer documentation detailing iOS 12’s SMS and call spam reporting, the extension provides a consistent way for users to report selected phone calls and incoming texts to third-party spa apps, and for their developers to receive crucial call metrics.
After downloading a call-blocking app from App Store that ships with an Unwanted Communication extensions, the user has to enable the extension manually through Settings → Phone → SMS/Call Reporting in their Settings app.
User reports a nuisance phone call or unwanted SMS/MMS message
This is where you’ll see all SMS and call-reporting extensions that are available to you on this device. You can only turn on one Unwanted Communication extension at a time.
Reporting SMS & call spamThe user can easily report any unwanted call by swiping left on an unknown or spammy number in the Phone app’s Recents list to pull up a new Report option. For texts, you can press the Report Messages button when it appears in the Messages transcript or simply press the text with 3D Touch to reveal the option in the shortcuts menu.
For whole conversations, swipe left on the thread in Messages to reveal a Report option or long-press a text to select additional messages, then choose the option Report Messages.
iOS launches the Unwanted Communication extension you installed, which goes to work gathering additional information before deciding whether to report or block the number.
Here’s what the Unwanted Communication extensions typically collect:
SMS: For received SMS messages that you have reported, the Unwanted Communication extension receives all of the text, content and sender information.
Call: For received calls that you have reported, the Unwanted Communication extension collects things like the caller’s number and the time of the call.
After manually reporting a nuisance call or SMS message, iOS 12 calls the Unwanted Communication extension which presents its custom controls to gather data from you.
You can then decide to enter all of the information that the extension requires and tap a Done button, or hit a Cancel button to abort the operation. To protect user privacy, the system always deletes all collected data after the extension terminates.
Blocked SMS or call number is added to your Blocked Contact list, managed in:
Messages: Settings → Messages → Blocked
Phone: Settings → Phone → Call Blocking & Identification
FaceTime: Settings → FaceTime → Blocked.
It’s important to reiterate that iOS 12’s new Unwanted Communication extension only works with SMS/MMS texts and phone calls. But what about VoIP calls and iMessages, you ask.
Well, your existing spam apps that are compatible with iOS 10’s CallKit framework already handle VoIP spam, while Apple has its own features for reporting iMessage spam.
What about privacy?As mentioned earlier, when you set up a third-party provider’s spam filter extension on your device, the filter provider is able to access all of the text and content including any incoming SMS and MMS messages received from senders that are not in Contacts.
And therein lies the rub because your texts may include verification codes for services like Dropbox, codes from banks and other institutions and other confidential info. You’re only at risk if you mistakenly report a legitimate text as spam and your filter provider is a bad actor.
Incoming calls are never sent to third-party developers.
After you have responded to a text three times or have added the sender to your Contacts, messages from that sender will no longer be passed to the filter provider for verification.
Your two centsWhat are your feelings on the new Unwanted Communication extension in iOS 12?
Have you used iOS’s existing blocking and reporting functions? If so, should Apple do more in terms of helping users report nuisance calls, do you think?
Secondary Mail Records Invite Spam
Many companies are locked in a death struggle with spam. Unfortunately, a simple error in your e-mail setup can allow spam to flood your inbox almost unchallenged.
I found this out the hard way, although the solution quickly became obvious. Fortunately, it’s something that almost every company can easily fix, in case the problem is affecting you.
If you have your own Internet domain name, or your company runs an e-mail server, this applies to you. If not, you probably know someone who could use the information below.
It’s common for companies to post a record for a second server as well. This server is said to have a secondary MX record. If the primary mail server is down or too busy to accept messages, the secondary server will be contacted instead by machines trying to send mail. The secondary server will accept the messages and eventually route them to the primary server when it’s once again available. (For technical details, see this Sendmail tutorial.)
Now that you know the basics, you’ll be able to see how spam can pour in if all of this isn’t properly set up.
Opening the Back Door to Spam
Laying out a plan to test antispam appliances, a developer who works in my company decided to assign each device, one at a time, to a second IP address. We duly changed our primary MX record to that second address: 67.40.30.51. (Let’s call this 51.) Within a few days, every mail server on the Internet had cleared the old number out of its cache and was sending our e-mail to the new number.
At this point, any antispam appliance being tested on our 51 address would do its thing, quarantining messages judged to be spam. It would then route the remaining good mail to our real mail server on the 50 address. So far, so good.
The spammers were working the angles like this:
• Primary mail server. Spammers were sending messages to numerous different e-mail addresses, most of them nonexistent, via our primary MX record. Since the primary MX record was now an antispam appliance we were testing, this spam was mostly detected by the appliance and blocked.
• Secondary mail server. Since the spam hadn’t been delivered to the primary MX record, spam servers simply looked up our secondary MX record and delivered the messages there. The real mail server at 50 readily accepted the messages, since the antispam appliance at 51 had been circumvented.
• Old subdomain names. As a result, we quickly deleted 50 as a secondary MX record. Mail servers should then try to send mail only to our primary MX record at 51, where our antispam appliance operates. But many spam servers simply clung to the fully qualified name of our mail server, Northwind. The spam servers continued sending spam directly to the machine at that subdomain name — ignoring the Internet mail protocol, which establishes the MX record as the standard.
A Fast Fix to a Frustrating Problem
Prior to our latest device tests, our mail server had been defended by no antispam appliance. We had configured it to avoid most spam by rejecting any mail sent to nonexistent addresses. It had also been told to automatically drop connections from known spam servers found on Spamhaus.org’s SBL+XBL block list. This reduced the spam we received to manageable levels.
Now that our mail server was on a separate IP address from whatever antispam appliance was currently being tested, however, stronger measures were needed. If your company has a secondary MX record pointing to a backup mail server, you may need to take the following steps, just as we did:
• Delete the secondary MX record. It’s usually not necessary for smaller companies to post a secondary MX record these days, with a mail server that’s at all reliable. Servers that send Internet mail will generally re-try a down server for up to 72 hours before giving up. Unless your mail server conks out for days at a time, these re-tries should be sufficient for you not to miss any mail, even if you have brief outages.
• Protect your secondaries. If your company truly does have redundant mail servers, go ahead and post secondary MX records for them. Any secondary machine, though, must have antispam protection that’s just as strong as the primary machine’s.
• Block inbound mail except from your filter. We configured our firewall to accept e-mail connections only from the antispam appliance at 51. Doing this clobbered the spam servers that were “remembering” our mail server’s IP address and subdomain name (after its secondary MX record was deleted). Good mail servers observed the standard Internet protocol and sent mail through the primary MX record. Spam servers, which don’t follow the rules, couldn’t get in through the back door.
Conclusion
With all of the obscure conventions and jargon of the Internet mail system, it’s not surprising that mail servers can get set up wrong. If that’s the case in your company, spammers are happy to drive right through the hole and deliver plenty of junk to your inboxes.
(For more on protecting your mail server, see my Jan. 24 column.)
An Executive Tech update on “Fixing Elections”
I wrote on Dec. 20, 2005, that two Florida counties had scrapped Diebold-brand electronic vote-counting equipment after computer experts found that results could be changed without detection. I noted later in that article, “Diebold memory cards became an issue in Ohio after the 2004 Presidential election. Secretary of State Kenneth Blackwell ordered the cards and other election records sealed from public inspection until after the state’s electors were sworn in.”
On Dec. 21, Carlo LoParo, a spokesman for the Ohio Secretary of State, e-mailed me, saying, “Diebold electronic voting machines were NOT in use in Ohio during the 2004 election. Further, the story you referenced relates to Ohio law requiring ballots be sealed for a period of 11-15 days after an election to allow for the arrival of overseas absentee ballots. (Please see Ohio Revised Code 3505.32.) This process does not relate to ‘electors’ or the Electoral College.”
I respectfully disagree with these statements.
• The Dayton Daily News and other news outlets reported on Dec. 12, 2004, that election records had been sealed by the Ohio Secretary of State. This was 40 days after the Presidential election, long after the normal 11-to-15-day period. The Daily News reporter wrote: “This period usually lasts about 10 days after the election, but was being extended because an official recount is under way in the state, according to Blackwell spokesman Carlo LoParo.” The final determination of contests for Presidential electors was on Dec. 7, 2004, based on federal law, and Presidential electors voted in each state on Dec. 13, 2004.
Bob Fitrakis, an Ohio attorney who formerly was involved in litigation with the Secretary of State, said in an interview regarding Diebold election services, “GEMS, which is Diebold software, was used to count votes on equipment in about half the counties.” Fitrakis edits the Columbus Free Press.
I would also like to acknowledge the research assistance provided by Mark Crispin Miller, the author of Fooled Again, an October 2005 book that criticizes election practices observed in Ohio and other U.S. states in the 2004 elections.
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