How to block external email from domains or individual email

To configure ZIMBRA to reject external email addressed to users in the system, or blacklist email, follow these steps.

1. Configure smtpd_sender_restrictions as shown below. ZIMBRA 7: Run:

$ zmlocalconfig -e postfix_smtpd_sender_restrictions="hash:/opt/zimbra/postfix/conf/postfix_reject_sender"

ZIMBRA 8.0: Add “client_sender_access hash:/opt/zimbra/postfix/conf/postfix_reject_sender” to /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf. ZIMBRA 8.5 and 8.6: Edit /opt/zimbra/conf/zmconfigd/smtpd_sender_restrictions.cf and insert the following text on line 2.

%%contains VAR:zimbraMtaSmtpdSenderRestrictions check_sender_access lmdb:/opt/zimbra/postfix/conf/postfix_reject_sender%%

Then run:

$ zmprov ms `zmhostname` +zimbraMtaSmtpdSenderRestrictions "check_sender_access lmdb:/opt/zimbra/postfix/conf/postfix_reject_sender"

2. Create /opt/zimbra/postfix/conf/postfix_reject_sender, containing a list of email addresses or domains to block, followed by REJECT, as in the example.

  [email protected] REJECT
domain.com REJECT

3. Run postmap to create the database and restart postfix.

$ /opt/zimbra/postfix/sbin/postmap /opt/zimbra/postfix/conf/postfix_reject_sender
$ zmmtactl stop && zmmtactl start

** You can use Amavis for blacklisting instead.