Email Network Security Blog

Why Not Use “mail.yourdomain.com” as the Name for Your Mail Server

Spammers will ignore MX records sometimes and use “mail.somedomainname.com” to relay spam to. If you have an off-site email filtering service provider and you set all your MX records to their server, all your mail should go to the off-site email filtering provider’s servers, according to the MX records, but this is not always the case. Spammers are smart enough to send spam directly to any machine named “mail.somedomainname.com”, because usually it is a mail server which will accept and handle mail for “somedomainname.com“, whether it is an MXed SMTP relay or not.

If you take the Best Practice Recommendation of Sentinare Messaging Solutions, you will also block SMTP port 25 inbound to your mail server and spammers won’t be able to hit your mail server anyhow, but this is also another best practice and another layer of security. There are some times that you can’t block SMTP port 25 inbound to your mail server, and in these cases you want to at least give your mail server a name other than “mail.somedomain.com”.