Get your DMARC going

Get your company implementing DMARC now…

During the past 5-6 years email industry efforts have been pushing the DMARC standard along. It provides the best widely supported and seemingly efficient way to – as a domain-owner – protect the domain from misuse and abuse in terms of spam and phishing attacks.

postkasse_japanAs sending email has often been a wild-west, and knowing who is a valid sender of email may prove a challenge for many companies – and as most IT developers does seem to care too much about the finer details of email (and production just as bad email headers as HTML markup 🙂 ), implementing DMARC protection on your domain may actually be a challenge.

The DMARC standard provide you 3 powerful tools:

  • Using DMARC you have the power (through) DNS to declare which mail-servers are valid senders of email from your domain.
  • The DKIM signing of mails allows your to prove to recipients it was sent from a valid server.
  • Finally DMARC  provides a way for the email receiver to report back to the sender about messages that pass and/or fail DMARC evaluation.

In summary, you have the option to protect the credibility of your domain (by not exposing it to spam and phishing), and you should care now, as Google through Gmail seems to be starting to push harder to signal which email is “safe” (or legitimate at least).

This latter effort will not only remove fake emails pretending to be from your domain, but it will likely also promote your legitimate emails and make them more likely to reach their audience.

Here are a few articles on how to get on with DMARC implementation:



Viewing EML files

As mails bounch around some email programs (I’m looking at you, Microsoft), seems to encrypt package forwarded mails in attachments with the extension .eml.

On Linux…

While Mozilla Thunderbird should be able to read them (as should Evolution), it requires you have the mail  application available on your machine, but I haven’t – I’m doing just fine with GMail in the browser. So far the best solution I’ve find – assuming it’s trivial non-sensitive, personal files – that an Online viewer seems to work pretty well. My preferred solution is the free one from encryptomatic. It handles the mails quite nicely, it restores the formatting to something quite readable and even handles embedded images and attachments within the eml-file.

On Windows…

If you’re using Windows Live Mail or any other mail application running on windows, it can probably handle the .eml files. An other option is to look for an App, as there seems to exist several apps on windows, which renders the .eml files with no issues.

A little trick (with a browser)

When using windows – even in a VirtualBox – there’s an easy little trick you can use: Save the file and simply rename the file extension from “.eml” to “.mht” and open the file with Internet Explorer. It should render perfectly.

Once the .eml file is renamed to .mht Google Chrome and Firefox seems able to render the contents too – though handling images and attachments seems much less graceful.

Salvaging a deleted message from Thunderbird

undeleteSuppose you got an important mail, but by accident deleted the message – and to make matters worse, you also decided that emptying the mailbox was a pretty neat idea. Is then time to Panic?

Well it might, but there is a chance you might be able to undelete the message – and quite easily if you’re on a Mac or a Linux machine. Here are the few steps, which has helped recover a lost mail or two… First close Thunderbird. Then located the mail directory (on Linux it’s located in the subdirectory .mozilla-thunderbird in you home directory – on windows most likely somewhere in C:\Documents and Settings\*\Application Data\Thunderbird – In there you’re looking for the “Local Folders” directory.

If you’re on a Mac or Linux type the following:

cat Trash | grep -v X-Mozilla- > Restored

The cat command prints all the line in the file Trash – not to the screen, but as input to grep. Grep is used to find all lines not begining with “X-Mozilla-“ and prints these – and the greater than makes the print go to a new file called Restored.

Once this is done exit the directory and restart Thunderbird. You should now be able to find a new folder called “Restored” and a lot of old mail. Find the message you need to restore, and drag it into the inbox or wherever you need it – then delete the “Restored” folder.

If you’re on windows you need to do a little more work. The trick happening with the command line above, is that all lines beginning with “X-Mozilla-” is deleted and thus restored from their deleted state. A suitable editor might do the trick.

Do notice, that the Trash folder may be quite large, if you haven’t run the “Compact Folders” in quite a while – and if you did do that after deleting the message you’re trying to restore, then it’s probably gone for good.

Tip a friend – not so simple

Many online sites such as news-sites and other content providers often have a “tip a friend” option. With this you can mail a friend and tell them about an interesting piece of content you’ve found. The Idea seems quite simple, and everyone should have the tip-option, wright? – no, wrong. While it may offer a convenience for some, it has several backsides.

First if you – or your email provider – has implemented anti-spam techniques such as SPF-records, the “tipping mail” will not be sent through the authorized list of mail-servers and thus have a larger likelihood of being labeled as spam. Your mail be sent, but you don’t know if it will arrive in your friends mailbox.

Second having two (assumable) valid email addresses submitted to a site could be a goldmine for evil spammers. Besides mailing the tip, the email addresses may be collected and abused some time in the future.

Third by having a site sending thousands and thousands of “tips” to friends does mimic a spammers’ behavior – the function may cause your servers to be labeled as a spamming server, and you may not be able to send mails – no tips nor important messages your servers may try to mail to you or other users.

If you want to have a “Tip a friend” function – make sure it’s a mailto-link.

The mailto-link may not be as sexy as the options available when you create the mails server side, but the links go out from the users’ own mail client and the likelihood of it being labeled as spam is far less. It also gives the user complete control of what is being sent – no unexpected ads or anything else unwanted material.

There is something good about spam

Now usually spam is evil, annoying and a bloody pain. It does however have rare moments of actual usefulness. On an average day my mailbox seems to be stormed by more than two hundred spam mails from just about every where on the planet. Thanks to server-side filters combined with mozillas learning filters, they all seem to disappear into a consolidated spambox. I can check the box (too look for any false positives), and if the box hasn’t gotten any new mail for more than an hour, something is most likely wrong in my mail setup.