SmarterMail supports Greylisting feature to prevent spam emails.  This feature essentially bounces all unknown message trying to connect to mail server  the first time.

The basis is that SPAMMERs create scripts to send spam automatically. These messages are then bounced back to their sending email server. Because most Spammers email does not come from a valid email server, the messages are not retried and therefore this reduces the amount of SPAM that your customers receive.

For those messages that are returned to valid email servers, the messages will be retried at least four times. When retried, the message is passed to the Mail Spool and it goes through its normal processing.  A record is also created that says this is a valid email address and keeps it for 36 days (default).  If another email from the same email address is received within the 36 day, record clock is reset for an additional 36 days and delivered directly to the Spool.

Emails from Trusted Senders and White listed IP will automatically bypass Greylisting and are delivered directly to the Spool.

Greylisting reduces the amount of spam by 90% before they hit the mail server.

Greylisting is enable by default for all email accounts. If you wish to disable this feature (not recommended), please follow the steps

1. Login into the SmarterMail webmail
2. Select Settings - Account Settings
3. Select Disable Greylisting, then Save.