Greylisting Enabled in SmarterMail Servers

We will soon begin enabling another anti-spam feature to SmarterMail 4 called greylisting, beginning Monday, May 21. Greylisting is a method of blocking spam based on the behavior of an email's sending server.

Put simply, when greylisting is enabled, a mail account will temporarily reject or bounce emails from unrecognized or unknown senders. For legitimate email, the sending server will attempt to send the email a second time, in which case the receiving server will process the email as per usual.

Therefore, greylisting will significantly reduce spam as the underlying idea behind greylisting is that spammers will not bother to attempt to send an email more than once to any given email account. However, this efficiency also can lead to initial (though generally brief) delivery delays once a sender emails an account with greylisting activated. The length of time an email is delayed is purely dependent on the time set on the sending server for re-sending an email.

Please realize that this will only happen on the first message from a given sender not listed on your trusted senders list. Once a sender passes this test the first time, they then get added to greylisting's trusted sender list. If a message is received from someone on the trusted senders list, the message bypasses greylisting completely and is then processed by SpamAssassin and our anti-virus settings and then delivered.  E-mail addresses can be manually be added to the trusted senders list. This can be done within SmarterMail under the Spam Filtering settings, both at the user and domain level.

To reiterate, greylisting will automatically be enabled on May 21 and requires no action from webmasters who administer the e-mail system. If you have any questions or concerns, please contact us at or 301-475-1900.