Wondering how to resolve ‘Postfix address already in use’ error in Plesk? We can help you.

As part of our Server Management Services, we assist our customers with several Plesk queries.

Today, let us discuss how to resolve this error.

How to configure postfix in Plesk?

Prerequisites

• You need to know the hostname of the SMTP server which is going to relay the mail for your mail server, which is smtprelay.snel.com in our case.
• You need to have the SSH login details of your server ready

 
Let us see the steps followed by our Support Techs to configure postfix in Plesk.

Step 1: Log in with SSH as root.

Step 2: Configure the MTA

Update the postfix configuration by issuing the following commands:

postconf -e 'relayhost = [smtprelay.snel.com]:25'
postconf -e 'smtp_tls_security_level = may'

Step 3: Restart the mail server

Restart the mail server by issuing the following command:

service postfix restart

Postfix address already in use error in Plesk

First and foremost let us see some of the symptoms of the error.

• Firstly, unable to start postfix.

It fails with the error below in /var/log/maillog log file:

postfix/postfix-script[9889]: starting the Postfix mail system
postfix/master[9890]: fatal: bind 0.0.0.0 port 25: Address already in use

• Manual start for smtp service fails:

# plesk bin service –start smtp
ERR [util_exec] proc_close() failed [‘/opt/psa/admin/bin/mailmng-service’ ‘–start-service’ ‘–mail-component=mta’] with exit code [1] mailmng-service failed: exit status 1

Above error is caused due to wrong configuration entries in /etc/postfix/master.cf

How to resolve postfix address already in use error in Plesk?

Let us see the steps followed by our Support Techs to resolve this error.

• Firstly, connect to the server via SSH
• Then, verify that another application is not using port 25 (output should be exactly as below):

# netstat -ntpl | grep 25
tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 21078/master
tcp6 0 0 :::25 :::* LISTEN 21078/master

• If output is different and a 3rd-party service is running, kill the process:

# kill -9 <id>

• Edit file /etc/postfix/master.cf and comment out all duplicate lines in the configuration, for example:

203.0.113.2- unix – n n – – smtp -o smtp_bind_address=203.0.113.2 -o
smtp_bind_address6= -o smtp_address_preference=ipv4

• Save the changes and close the file.
• Finally, restart Postfix to apply the changes:

service postfix restart

Please note the line with the IP address should exist only once in the /etc/postfix/master.cf configuration file.

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Conclusion

In short, today we saw how our Support Techs resolved Postfix address already in use error in Plesk.