How to check if your email server looks like a spam source

Taking full control of your own email, that is running your own email server, is a must if you really care about privacy, security or maximum customization.

Taking full control of your own email, that is running your own email server, is a must if you really care about privacy, security or maximum customization.

When you start doing it though, you soon find out that the hardest, or at least lest documented task, is not how to send email, or how to block spam. It is how to make sure that the email you send is always accepted by other sites, that is how to find out if your email server looks like a spam source.

Here is a list of tips that I used to check this part of my configuration. I got them from a thread on the postfix mailing list and a couple other sources. Almost all the information below is applicable no matter which email server you use.

  • Check the IP address of your email server to see if it’s on any black list at OpenRbl or Blacklist Alert, that queries many databases
  • Check your DNS for any misconfigurations
  • Check online if your server is an open relay. And also check the same thing by yourself, for example using telnet from an external network (3rd party open relay test are handy, but double-checking is a must in these cases).
  • On the same note, you can also perform some of the tests above on the SMTP Diagnostics page
  • Set up DKIM and SPF on your outgoing email (here is atutorial for DKIM and SPF with Postfix)
    • (update 2010/05/17) Check the discussion at LinuxToday about this tip to know more about what happens when your email server is put by somebody’s incompetence or mistake on a black list (as from time to time also happens to me, by the way!).

      Note 1: I do know that using DKIM and/or SPF to accept or reject incoming email is a very controversial issue that can start flamewars among email administrators. Using them for the email you send, instead, should have no side effects. In my case, it also was the only way to have my email accepted by some big providers like Hotmail or Yahoo, that is providers that are used by too many people to snob them, regardless of what we think of their services.

      Note 2: Did I forget anything? If I did, please register and add it in the comment, or just send me an email to mfioretti, at nexaima, dottt net.