====Send E-mail via Relay from Zimbra 8.8====
https://wiki.zimbra.com/wiki/Outgoing_SMTP_Authentication \\
https://wavemotiondigital.com/2020/03/30/zimbra-smtp-relay-for-multiple-domains-via-mailgun-or-other-provider/ \\
https://www.smtp2go.com/setupguide/zimbra-mta-8-7/ \\

First you'll need a relay service/smart host with a user name and a password to send through.

==Set the Relay Host==
<code>
zmprov ms `zmhostname` zimbraMtaRelayHost mailrelay.example.com
</code>

Reboot the ASSP server host, seems to be needed or I'm impatient.

==Enable SMTP Authentication==
<code>
echo mailrelay.example.com username:password > /opt/zimbra/conf/relay_password
</code>
Create a postfix lookup table:
<code>
postmap /opt/zimbra/conf/relay_password
</code>
Test that the lookup table is correct, the following should return username:password:
<code>
postmap -q mailrelay.example.com /opt/zimbra/conf/relay_password
</code>
Configure postfix to use the new password map:
<code>
zmprov ms `zmhostname` zimbraMtaSmtpSaslPasswordMaps lmdb:/opt/zimbra/conf/relay_password
</code>
Configure postfix to use SSL authentication:
<code>
zmprov ms `zmhostname` zimbraMtaSmtpSaslAuthEnable yes
</code>
Configure postfix to use the outgoing servername rather than the canonical server name:
<code>
zmprov ms `zmhostname` zimbraMtaSmtpCnameOverridesServername no
</code>
Enable Plain Text Authentication (we will use TLS to protect it)
<code>
zmprov ms `zmhostname` zimbraMtaSmtpSaslSecurityOptions noanonymous
</code>
Enable TLS:
<code>
zmprov ms `zmhostname` zimbraMtaSmtpTlsSecurityLevel may
</code>