# Switch to user Zimbra
su zimbra
# Add credentials to relay_password file:
vi /opt/zimbra/conf/relay_password
# Add:
smtp.sendgrid.net yourSendGridUsername:yourSendGridPassword
# Apply configuration to Zimbra
postmap /opt/zimbra/conf/relay_password
postmap -q smtp.sendgrid.net /opt/zimbra/conf/relay_password
zmprov ms `zmhostname` zimbraMtaSmtpSaslPasswordMaps lmdb:/opt/zimbra/conf/relay_password
zmprov ms `zmhostname` zimbraMtaSmtpSaslAuthEnable yes
zmprov ms `zmhostname` zimbraMtaSmtpCnameOverridesServername no
zmprov ms `zmhostname` zimbraMtaSmtpTlsSecurityLevel may
zmprov ms `zmhostname` zimbraMtaSmtpSaslSecurityOptions noanonymous
zmprov ms `zmhostname` zimbraMtaRelayHost smtp.sendgrid.net:587
Now wait for a couple of minutes and start testing it by sending out some test mails.
Follow the log file to see if it works or not:
tail -f /var/log/zimbra.log