Tighten up your Exim (mail server)

For WHM versions 11.27/11.28

You may want to prevent users from bypassing your mail server to send mail. This feature allows you to configure your server so that the mail transport agent (MTA), Mailman mailing list software, and root user are the only accounts able to connect to remote SMTP servers.

To enable or disable users from bypassing your mail server:
Click Enable or Disable.

Please make sure that SMTP Tweak is turned on:

/scripts/smtpmailgidonly on

It’s also a good idea to require sender verification, which can be enabled in WHM >> Exim Configuration Editor

How to send mails to domains having MX record as IP using Exim?

In this example, domain.com has MX record as IP and not FQDN, see below
domain.com. 3600 IN MX 10 XX.XX.XX.XX.

By default, Exim configured on Cpanel does not allows to send mails to domains having MX records as IP

Fix:-

You will need to add entry "allow_mx_to_ip = yes" into the exim.conf as shown below,

# If you want Exim to support the "percent hack" for all your local domains,
# uncomment the following line. This is the feature by which mail addressed
# to x%y@z (where z is one of your local domains) is locally rerouted to
# x@y and sent on. Otherwise x%y is treated as an ordinary local part.
# percent_hack_domains = *
allow_mx_to_ip = yes
#sender_host_accept = +include_unknown:*
#sender_host_reject = +include_unknown:lsearch*;/etc/spammers

then fire command

#service exim restart

Delete Spam from Exim Queue

Spam is a major cause of headache for many people in the world. Especially server administrators.

Here is a tip to clean up your exim mail queue if its getting to large and full of spam.

Please keep in mind that some legitimate emails may get deleted by this method. Please use it carefully. I had more than 2000 emails in my queue, and it was reduced to about 50 after running a few of these.

First, run

grep -R -l [SPAM] /var/spool/exim/msglog/*cut -b26-xargs exim -Mrm

The highlighted word will be used in a grep search and replace and all messages matching that will be deleted. If you also want to remove frozen messages from your queue, run the following

grep -R -l '*** Frozen' /var/spool/exim/msglog/*cut -b26-xargs exim -Mrm

You can perform one more that will also clean your exim queue some more

grep -R -l 'The recipient cannot be verified' /var/spool/exim/msglog/*cut -b26-xargs exim -Mrm

Second tip - if you are using CPanel, set up your mails to default to :fail: rather than :blackhole: