Introduction

Linux Postfix troubleshooting refers to the process of identifying and resolving issues related to the Postfix mail server on a Linux system, such as problems with sending or receiving emails, configuration errors, and other related issues.

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Task Details

Some users of the monitoring app have reported issues with the xFusionCorp Industries mail server. They have a mail server in Stork DC where they are using a postfix mail transfer agent. Postfix service seems to fail. Try to identify the root cause and fix it.

Perform the below commands based on your question server, user name & other details might differ. So please read the task carefully before executing it. All the Best 👍

Solution:

1. Login on the Mail server as per the task and switch root user

thor@jump_host /$ ssh groot@stmail01

The authenticity of host 'stmail01 (172.16.238.11)' can't be established.

ECDSA key fingerprint is SHA256:SySamszyWhhLGFiybhGBqfrr8g55wS/3e37ZpBOvICs.

ECDSA key fingerprint is MD5:6d:31:18:2a:f9:07:f3:29:dd:0a:d3:1f:6e:04:0a:db.

Are you sure you want to continue connecting (yes/no)? yes

Warning: Permanently added 'stmail01,172.16.238.17' (ECDSA) to the list of known hosts.

groot@stmail01's password:

[groot@stmail01 ~]$ sudo su -

 We trust you have received the usual lecture from the local System

Administrator. It usually boils down to these three things:

     #1) Respect the privacy of others.

    #2) Think before you type.

    #3) With great power comes great responsibility.

 [sudo] password for groot:

[root@stmail01 ~]#

2. Start postfix service, check the status with -l for details error output

[root@stmail01 ~]# systemctl start postfix

Job for postfix.service failed because the control process exited with error code. See "systemctl status postfix.service" and "journalctl -xe" for details.

[root@stmail01 ~]#

[root@stmail01 ~]# systemctl status postfix -l

● postfix.service - Postfix Mail Transport Agent

   Loaded: loaded (/usr/lib/systemd/system/postfix.service; enabled; vendor preset: disabled)

   Active: failed (Result: exit-code) since Tue 2021-06-22 14:55:33 UTC; 6s ago

  Process: 383 ExecStart=/usr/sbin/postfix start (code=exited, status=1/FAILURE)

  Process: 382 ExecStartPre=/usr/libexec/postfix/chroot-update (code=exited, status=0/SUCCESS)

  Process: 379 ExecStartPre=/usr/libexec/postfix/aliasesdb (code=exited, status=75)



Jun 22 14:55:31 stmail01.stratos.xfusioncorp.com systemd[1]: Starting Postfix Mail Transport Agent...

Jun 22 14:55:31 stmail01.stratos.xfusioncorp.com aliasesdb[379]: /usr/sbin/postconf: fatal: parameter inet_interfaces: no local interface found for ::1

Jun 22 14:55:32 stmail01.stratos.xfusioncorp.com aliasesdb[379]: newaliases: fatal: parameter inet_interfaces: no local interface found for ::1

Jun 22 14:55:32 stmail01.stratos.xfusioncorp.com postfix/sendmail[381]: fatal: parameter inet_interfaces: no local interface found for ::1

Jun 22 14:55:32 stmail01.stratos.xfusioncorp.com postfix[383]: fatal: parameter inet_interfaces: no local interface found for ::1

Jun 22 14:55:33 stmail01.stratos.xfusioncorp.com systemd[1]: postfix.service: control process exited, code=exited status=1

Jun 22 14:55:33 stmail01.stratos.xfusioncorp.com systemd[1]: Failed to start Postfix Mail Transport Agent.

Jun 22 14:55:33 stmail01.stratos.xfusioncorp.com systemd[1]: Unit postfix.service entered failed state.

Jun 22 14:55:33 stmail01.stratos.xfusioncorp.com systemd[1]: postfix.service failed.

[root@stmail01 ~]#

3. As we identify the issue in the configuration file, make the changes

[root@stmail01 ~]# cat /etc/postfix/main.cf |grep inet_interface

# The inet_interfaces parameter specifies the network interface

inet_interfaces = all

#inet_interfaces = $myhostname

#inet_interfaces = $myhostname, localhost

inet_interfaces = localhost

# the address list specified with the inet_interfaces parameter.

# receives mail on (see the inet_interfaces parameter).

# to $mydestination, $inet_interfaces or $proxy_interfaces.

# - destinations that match $inet_interfaces or $proxy_interfaces,

# unknown@[$inet_interfaces] or unknown@[$proxy_interfaces] is returned

[root@stmail01 ~]#

[root@stmail01 ~]# vi /etc/postfix/main.cf

[root@stmail01 ~]# cat /etc/postfix/main.cf |grep inet_interface

# The inet_interfaces parameter specifies the network interface

inet_interfaces = all

#inet_interfaces = $myhostname

#inet_interfaces = $myhostname, localhost

#inet_interfaces = localhost

# the address list specified with the inet_interfaces parameter.

# receives mail on (see the inet_interfaces parameter).

# to $mydestination, $inet_interfaces or $proxy_interfaces.

# - destinations that match $inet_interfaces or $proxy_interfaces,

# unknown@[$inet_interfaces] or unknown@[$proxy_interfaces] is returned

[root@stmail01 ~]#

4. Post the configuration saved start the services and check the status

root@stmail01 ~]# systemctl start postfix

[root@stmail01 ~]#

[root@stmail01 ~]# systemctl status postfix

● postfix.service - Postfix Mail Transport Agent

   Loaded: loaded (/usr/lib/systemd/system/postfix.service; enabled; vendor preset: disabled)

   Active: active (running) since Tue 2021-06-22 14:59:45 UTC; 16s ago

  Process: 475 ExecStop=/usr/sbin/postfix stop (code=exited, status=0/SUCCESS)

  Process: 504 ExecStart=/usr/sbin/postfix start (code=exited, status=0/SUCCESS)

  Process: 503 ExecStartPre=/usr/libexec/postfix/chroot-update (code=exited, status=0/SUCCESS)

  Process: 501 ExecStartPre=/usr/libexec/postfix/aliasesdb (code=exited, status=0/SUCCESS)

 Main PID: 575 (master)

   CGroup: /docker/050a5d787eedc1731e809d002d6f548be599723012d6b80fd344d807a45da4db/system.slice/postfix.service

           ├─575 /usr/libexec/postfix/master -w

           ├─576 pickup -l -t unix -u

           └─577 qmgr -l -t unix -u

 Jun 22 14:59:45 stmail01.stratos.xfusioncorp.com systemd[1]: Starting Postfix Mail Transport Agent...

Jun 22 14:59:45 stmail01.stratos.xfusioncorp.com postfix/master[575]: daemon started -- version 2.10.1, configuration /e...fix

Jun 22 14:59:45 stmail01.stratos.xfusioncorp.com systemd[1]: Started Postfix Mail Transport Agent.

Hint: Some lines were ellipsized, use -l to show in full.

[root@stmail01 ~]#

5. Validate the task

hor@jump_host /$ telnet stmail01 25

Trying 172.16.238.17...

Connected to stmail01.

Escape character is '^]'.

220 stmail01.stratos.xfusioncorp.com ESMTP Postfix

Connection closed by foreign host.

thor@jump_host /$

The command "telnet stmail01 25" attempts to establish a Telnet connection to the SMTP (Simple Mail Transfer Protocol) server running on the host "stmail01" on port 25, which is the default port used for sending email messages between servers.

Thank you so much for taking your valuable time to read

I took the initiative to learn in public and share my work with others. I tried my level best in squeezing as much information as possible in the easiest manner. Hope you learned something new today :)

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