Recommendations for detecting and reducing the
volume of spam received by MailEnable.DETAILS
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
- Do not have a catch-all set for domains. Spammers
will make up email addresses for the domains hosted and try to send to
- 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
- 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
- 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 22.214.171.124 from
Google then reverse DNS blacklisting will not work.
- Enable the URL blacklisting option, since it will
scan messages for URLs that are known to be spam links. Spamhaus Zen
blacklist is appropriate for this.
- Enable MailEnable's Sender Policy
Framework (not available in the Standard edition). This setting is
also configured under the properties of the SMTP Connector in the MailEnable
- Enable greylisting under the SMTP Connector
properties in the administration program (not available in the Standard
edition). This will reduce spam by delaying new messages briefly, since
spammers will generally not retry a delayed address.
- Create a filter to block emails that fail the DKIM
test (not available in the Standard edition).
- Bayesian Filtering is a self learning
spam system that uses complex algorithms to detect spam by comparing
message content against a dictionary. All filtering actions can
be executed on the Bayesian criteria being met.
- If using MailEnable Professional or Enterprise
Editions, configure one or more filters containing known spam term or word
patterns. For example, a filter containing terms like Viagra (and combinations
thereof using wildcards or text patterns) will catch mainstream
- There are several dedicated third party anti-spam
solutions that can be used to complement MailEnable's integrated spam blocking
and content filtering. These are outlined here: http://www.mailenable.com/kb/content/article.asp?ID=ME020344
Also, review the following articles regarding
reducing incoming spam.
Spam - Frequently Asked Questions:
Blacklisting methods: Article ME020084
Bayesian Filtering: Article ME020346