Howtos - SMTP Authentication to ISP
[edit] Overview
To protect against spam, some ISPs block outgoing connections on SMTP (port 25). In order to send mail from such an ISP, the Postfix mail server must be configured as an authenticated client to the ISP's mail server.
[edit] Add User Authentication Support to Mail Server Configuration
In /etc/postfix/main.cf, add the following to enable Postfix's authenticated mail client:
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options =
[edit] Add Username and Password Settings
The ISP's mail server, username, and password are kept in a separate file: /etc/postfix/sasl_passwd. The format is:
[hostname] username:password
For example:
[smtp.broadband.rogers.com] bob123@rogers.com:hockey
Anytime you add or change the /etc/postfix/sasl_passwd file, run the following command:
postmap /etc/postfix/sasl_passwd
[edit] Add Outbound Relay Host
Using the SMTP mail server configuration in the web-based configuration tool, add the ISP's mail server. In our example, smtp.broadband.rogers.com is used.
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