MailEnable provides an extensive array of spam blocking, and content filtering features that can be enabled to reduce the volume of received unsolicited e-mail or spam.

The following actions should be considered:

Do not have a catch-all set for domains.

Enable the setting 'Reject mail if sender address is from an invalid domain' . This is in the SMTP connector Security properties. This will stop the mail server from accepting email from people who have put an invalid domain as their From address.

Enable the option for requiring that those sending mail to the server have a DNS PTR record defined for the IP address of their mail server. This setting is configured under the properties of the SMTP connector in the MailEnable Administration Program. Not having a PTR record usually indicates that the sender is on a dial-up/cable/ADSL connection.
 
Enable the option to require that anyone sending from a locally hosted e-mail address needs to authenticate. This prevents spammers from using your local envelope sender to send spam to other users on your server. This setting is configured under the properties of the SMTP connector in the MailEnable Administration Program and is called address spoofing prevention.

Configure the SMTP connector to use one or two RDNS blacklist providers; since this will prevent you receiving spam from known spammer IP addresses. Spamhaus Zen and Barracuda blacklist are recommended. Be aware that you must register with Barracuda to use their blacklist. When using a blacklist, make sure you are using your own DNS IP address in your SMTP options. If you use an external DNS such as 8.8.8.8 from Google then reverse DNS blacklisting will not work.
 
Enable the URL blacklisting option.

Enable MailEnable's SPF (not available in the Standard edition). This setting is also configured under the properties of the SMTP Connector in the MailEnable Administration program.

Enable greylisting under the SMTP Connector properties in the administration program (not available in the Standard edition).

Create a filter to block emails that fail the DKIM test (not available in the Standard edition).

Enable Bayesian Filtering.

If using MailEnable Professional or Enterprise Editions, configure one or more filters containing known spam term or word patterns.

There are several dedicated third party anti-spam solutions that can be used to complement MailEnable's integrated spam blocking and content filtering. Ask us for more details.