How to configure sendmail for outgoing mail only
To configure Sendmail for outgoing mail only, you'll need to modify the Sendmail configuration file (sendmail.cf
or sendmail.mc
) to restrict its functionality to only sending mail and not accepting incoming mail.
Here are the general steps:
Step 1: Create a new configuration file
Create a new file, e.g., sendmail.mc
, in the /etc/mail
directory (or the equivalent directory on your system). This file will contain the modified configuration.
Step 2: Restrict incoming mail
Add the following lines to the sendmail.mc
file to restrict incoming mail:
define(`confSMTP_ACCEPT_MAX', `0')dnl
define(`confSMTP_ACCEPT_MIN', `0')dnl
define(`confSMTP_ACCEPT', `no')dnl
These lines set the maximum, minimum, and default values for incoming mail to 0, effectively disabling incoming mail acceptance.
Step 3: Configure outgoing mail
Add the following lines to the sendmail.mc
file to configure outgoing mail:
define(`confSMTP_SEND', `yes')dnl
define(`confSMTP_RELAYHOST', `your_smtp_server')dnl
Replace your_smtp_server
with the hostname or IP address of your SMTP server (e.g., your mail server or a third-party SMTP service).
Step 4: Update the Sendmail configuration
Run the following command to update the Sendmail configuration:
make -f /etc/mail/sendmail.mc sendmail.cf
This will generate a new sendmail.cf
file based on the modified sendmail.mc
file.
Step 5: Restart Sendmail
Restart the Sendmail service to apply the new configuration:
service sendmail restart
Alternatively, you can use the sendmail
command with the -q
option to reload the configuration:
sendmail -q
Verify the configuration
To verify that Sendmail is now configured for outgoing mail only, you can use the sendmail -bv
command to test the configuration:
sendmail -bv [email protected]
If everything is set up correctly, Sendmail should send a test email to the specified address.
That's it! Your Sendmail configuration should now be restricted to only sending outgoing mail.