How to block user from sending mail in postfix

To block a user from sending mail in Postfix, you can use various methods. Here are a few:

Method 1: Using smtpd_sender_restrictions

You can add a restriction to the smtpd_sender_restrictions parameter in the Postfix configuration file (main.cf) to block a specific user from sending mail. For example:

smtpd_sender_restrictions = check_sender_access hash:/etc/postfix/sender_access

Create a file /etc/postfix/sender_access with the following format:

[email protected] REJECT

This will block the user [email protected] from sending mail.

Method 2: Using smtpd_recipient_restrictions

You can also add a restriction to the smtpd_recipient_restrictions parameter to block a specific user from sending mail. For example:

smtpd_recipient_restrictions = check_recipient_access hash:/etc/postfix/recipient_access

Create a file /etc/postfix/recipient_access with the following format:

[email protected] REJECT

This will block the user [email protected] from sending mail.

Method 3: Using transport_maps

You can create a transport map to redirect mail from a specific user to /dev/null, effectively blocking them from sending mail. For example:

transport_maps = hash:/etc/postfix/transport_maps

Create a file /etc/postfix/transport_maps with the following format:

[email protected] discard

This will redirect mail from [email protected] to /dev/null, effectively blocking them from sending mail.

Method 4: Using sender_canonical_maps

You can create a sender canonical map to rewrite the sender address of a specific user to an invalid address, effectively blocking them from sending mail. For example:

sender_canonical_maps = hash:/etc/postfix/sender_canonical_maps

Create a file /etc/postfix/sender_canonical_maps with the following format:

[email protected] [email protected]

This will rewrite the sender address of [email protected] to [email protected], effectively blocking them from sending mail.

Remember to reload the Postfix configuration after making changes to the configuration files:

sudo postfix reload

Note that these methods may have varying levels of effectiveness, and you may need to combine them or use additional techniques to achieve the desired level of blocking.