Relay per Domain

Reference bug: http://bugzilla.zimbra.com/show_bug.cgi?id=32740

Zimbra allows relaying emails to a specific server only, i.e using zimbraMtaRelayHost. However, there are needs to relay emails per domain basis. For example, you want emails sent by users@domain1.com should be relayed through smtp.domain1.com and users@domain2.com through smtp.domain2.com servers. You can configure it using "sender_dependent_relayhost_maps".

This is an example and tested on ZCS 5.0.16

1. Add following line to /opt/zimbra/postfix/conf/main.cf

sender_dependent_relayhost_maps = hash:/opt/zimbra/postfix/conf/bysender

2. Create file /opt/zimbra/postfix/conf/bysender and enter your domain names and relay server's IP addresses.

@domain1.com  [10.10.10.1]
@domain2.com  [20.20.20.1]

You can even add individual email IDs to relay their emails to specific relay host.

 user@domain.com [10.10.10.2]

3. Create the hash file.

postmap /opt/zimbra/postfix/conf/bysender

4. Restart zmmtactl

zmmtactl stop
zmmtactl start

5. Test by sending emails.

Note: Above settings will not survive zimbra upgrades. Make sure you take backup of config files before upgrading.