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Below is the simple guide on how to configure Zimbra MTA (version 8.5 or later) to send outgoing emails using your SMTP2GO’s SMTP Server.

Step 1

Login to your server via SSH as ‘root’ user. We recommend to do the following steps as zimbra user.

su - zimbra

Step 2

Setting a relay host: Change the relay host to mail.smtp2go.com followed by port 2525 (8025, 587 and 25 can also be used).

zmprov ms `zmhostname` zimbraMtaRelayHost mail.smtp2go.com:2525

Step 3

Enabling SMTP authentication: Create a text file with the username/password. Replace USERNAME with your SMTP2GO Username and PASSWORD with your SMTP2GO password.

echo mail.smtp2go.com USERNAME:PASSWORD > /opt/zimbra/conf/relay_password

Step 4

Create a postfix lookup table:

postmap /opt/zimbra/conf/relay_password

Step 5

To test that the lookup table is correct, the following command should return the USERNAME:PASSWORD

postmap -q mail.smtp2go.com /opt/zimbra/conf/relay_password

Step 6

Configure postfix to use the new password map:

zmprov ms `zmhostname` zimbraMtaSmtpSaslPasswordMaps lmdb:/opt/zimbra/conf/relay_password

Step 7

Configure postfix to use SSL authentication:

zmprov ms `zmhostname` zimbraMtaSmtpSaslAuthEnable yes

Step 8

Configure postfix to use the outgoing server name rather than the canonical server name:

zmprov ms `zmhostname` zimbraMtaSmtpCnameOverridesServername no

Step 9

Enable to use TLS:

zmprov ms `zmhostname` zimbraMtaSmtpTlsSecurityLevel may

Step 10

Enable Plaintext Authentication: Remove the noplaintext option to enable the plaintext authentication:

zmprov ms `zmhostname` zimbraMtaSmtpSaslSecurityOptions noanonymous

Step 11

The latest update on configuration will be reflected automatically within 2 minutes.

Note: If you see an error ‘550 unable to verify sender address’ when trying to send an email after setting up, this means your ‘From’ email address doesn’t have a valid MX record setup yet. All emails must be sent from an email address that has an MX record at its domain name.

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