5 steps to configure your Postfix email server as to relay through ISP outbound service

ตัวอย่างขั้นตอนต่อไปนี้ เราสามารถแก้ไขคอนฟิกเพื่อ relay ไป Gmail ได้นะครับ

Postfix email server as to relay through ISP outbound service
Postfix email server as to relay through ISP outbound service

1. Create password maps file (it assigns username/passwords to specified mail servers).
You can choose any name, let’s say it is /etc/postfix/relay_passwd.
It’s content should be as follows:

relay.dnsexit.com USERNAME:PASSWORD

Note: Replace USERNAME and PASSWORD with your DNS EXIT mail relay username and PASSWORD.

2. Set proper permissions for that file:  

chown root:root /etc/postfix/relay_passwd

chmod 600 /etc/postfix/relay_passwd

3. Create hash from maps file (remember to do it each time you change your maps file):

postmap /etc/postfix/relay_passwd

4. Configure your /etc/postfix/main.cf:

relayhost = relay.dnsexit.com
smtp_fallback_relay = relaybackup.dnsexit.com
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/relay_passwd
smtp_sasl_security_options =

Note: If your ISP blocks outgoing port 25. You can choose to use alternative SMTP ports by appending the port at the end:
relayhost = relay.dnsexit.com:26

5. Reload or restart your postfix:  

/etc/init.d/postfix restart

Other notes about postfix:

If the above settings don’t work, you need to make sure the SASL support (smtp authentication) is compiled into Postfix. To do so, you may need to upgrade to latest version of Postfix.