If you have multiple ISPs and want to use their respective SMTP servers for sending mail from your Postfix server, you can configure authentication for each ISP separately. Here’s how you can set up SMTP authentication for multiple ISPs in Postfix:<\/p>\n
sasl2-bin<\/code> package if it’s not already installed:\n\n<\/div>\nsudo apt-get install sasl2-bin<\/span>
\n<\/code><\/div>\n<\/div>\n<\/li>\n- Create a new file in
\/etc\/postfix\/sasl<\/code> directory for each ISP you want to use. For example, if you want to use two ISPs, create the following files:\n\n<\/div>\n\/etc\/postfix\/sasl\/smtp1.conf
\n\/etc\/postfix\/sasl\/smtp2.conf
\n<\/code><\/div>\n<\/div>\n<\/li>\n- Add the following lines to each file, replacing
SMTP_SERVER<\/code> with the hostname or IP address of the ISP’s SMTP server, and USERNAME<\/code> and PASSWORD<\/code> with your authentication credentials:\n\n<\/div>\npwcheck_method: saslauthd<\/span>
\nmech_list: PLAIN LOGIN<\/span>
\nlog_level: 7<\/span>
\nauth_mech: plain login<\/span>
\nSMTP_SERVER USERNAME:PASSWORD
\n<\/code><\/div>\n<\/div>\n<\/li>\n- Make sure that the permissions on the new files are set correctly so that they can be read by the Postfix process:\n\n<\/div>\n
sudo chmod<\/span> 600 \/etc\/postfix\/sasl\/smtp*.conf
\n<\/code><\/div>\n<\/div>\n<\/li>\n- Edit the
\/etc\/postfix\/main.cf<\/code> configuration file and add the following lines to set up SMTP authentication:\n