Allow exim to relay mail

To allow Exim to relay mail, you need to configure it to accept incoming mail from other hosts and forward it to the final destination. Here are the general steps:

Step 1: Configure Exim to listen for incoming mail

In your Exim configuration file (usually /etc/exim.conf or /etc/exim4/exim.conf), add the following lines to allow Exim to listen for incoming mail:

# Listen for incoming mail
listen = * : 25

This tells Exim to listen for incoming mail on port 25 (the default SMTP port).

Step 2: Configure Exim to relay mail

To allow Exim to relay mail, you need to add a relayhost directive to your Exim configuration file. This specifies the host that Exim should forward the mail to. For example:

# Relay mail to the specified host
relayhost = your_smtp_server.example.com

Replace your_smtp_server.example.com with the hostname or IP address of the SMTP server that you want to relay mail to.

Step 3: Configure Exim to allow relaying

To allow relaying, you need to add a relay_from_hosts directive to your Exim configuration file. This specifies the hosts that are allowed to relay mail through Exim. For example:

# Allow relaying from the specified hosts
relay_from_hosts = 192.168.1.0/24

Replace 192.168.1.0/24 with the IP address range of the hosts that you want to allow to relay mail through Exim.

Step 4: Restart Exim

After making changes to your Exim configuration file, you need to restart Exim to apply the changes:

sudo service exim restart

Additional security considerations

To prevent abuse, you may want to consider adding additional security measures to your Exim configuration, such as:

• Setting a sender_verify directive to require sender verification
• Setting a recipient_verify directive to require recipient verification
• Configuring Exim to use a spamassassin filter to scan incoming mail for spam
• Configuring Exim to use a clamav filter to scan incoming mail for viruses

It's also a good idea to monitor your Exim logs to detect and prevent abuse.