Setup mail server on centos 7

This article helps you to install and configure basic mail server on Centos 7. Here i have used Postfix for SMTP, Dovecot for POP/IMAP and Dovecot SASL for SMTP AUTH.
Before proceeding please make sure you have assigned static IP for the server and have internet connectivity for installing packages.

Setup mail server on centos 7

1. Installing packages
2. Postfix configuration
3. Dovecot configuration
4. User creation

Installing packages

Step 1 » Assign hostname for the server using the below command.
[root@krizna ~]# hostnamectl set-hostname
Step 2 » Make a host entry with your IP in /etc/hosts file.
Step 3 » Now start installing packages.
[root@krizna ~]# yum -y install postfix dovecot
After package installation continue with postfix configuration.

Postfix configuration

First create SSL certificate for encryption.
Step 4 » Follow the below steps one by one for creation.
[root@mail ~]# mkdir /etc/postfix/ssl
[root@mail ~]# cd /etc/postfix/ssl
[root@krizna ssl]# openssl genrsa -des3 -out server.key 2048
[root@krizna ssl]# openssl rsa -in server.key -out server.key.insecure
[root@krizna ssl]# mv server.key
[root@krizna ssl]# mv server.key.insecure server.key
Leave blank for A challenge password [] value in the below step.
[root@krizna ssl]# openssl req -new -key server.key -out server.csr
[root@krizna ssl]# openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt

Step 5 » Now open /etc/postfix/ file for changes.
Find and uncomment the below lines.
#inet_interfaces = localhost #---> line no 116
#mydestination = $myhostname, localhost.$mydomain, localhost #--> line no 164

and add below lines at the end of the file. change myhostname and mydomain values with yours and home_mailbox value to your desired directory. Here it will store mails in the users home directory (Eg: /home/john/mail ).

Step 6 » Open /etc/postfix/ file, add the below lines after “smtp inet n – n – – smtpd” line.

Now check the configuration using postfix check command.
Step 7 » Now configure Dovecot SASL for SMTP Auth. Open /etc/dovecot/conf.d/10-master.conf file, find “# Postfix smtp-auth” line ( line no:95 ) and add the below lines.
# Postfix smtp-auth
unix_listener /var/spool/postfix/private/auth {
mode = 0660
user = postfix
group = postfix

Step 8 » Open /etc/dovecot/conf.d/10-auth.conf file, find “auth_mechanisms = plain” ( Line no: 100 ) and add login to the value like below.
auth_mechanisms = plain login
Step 9 » Postfix configuration is over. Now restart both postfix and dovecot services and enable auto start.
[root@mail ~]# systemctl restart postfix
[root@mail ~]# systemctl enable postfix
[root@mail ~]# systemctl restart dovecot
[root@mail ~]# systemctl enable dovecot

Step 10 » Add the firewall rules to allow 25, 587 and 465 ports.
[root@mail ~]# firewall-cmd --permanent --add-service=smtp
[root@mail ~]# firewall-cmd --permanent --add-port=587/tcp
[root@mail ~]# firewall-cmd --permanent --add-port=465/tcp
[root@mail ~]# firewall-cmd --reload
Now start testing connectivity for each ports 25,587 and 465 using telnet and make sure you are getting AUTH PLAIN LOGIN line after issuing ehlo command in telnet.
[root@mail ~]# telnet 465
Connected to
Escape character is '^]'.
220 ESMTP Postfix
ehlo <------- Type this command 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-STARTTLS 250-AUTH PLAIN LOGIN 250-AUTH=PLAIN LOGIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN

Dovecot configuration

Start configuring Dovecot .
Step 11 » Open /etc/dovecot/conf.d/10-mail.conf file, find #mail_location = (line no : 30 ) and add the same directory which is given to home_mailbox in the postfix config file ( Step 5).
mail_location = maildir:~/mail
Step 12 » Open /etc/dovecot/conf.d/20-pop3.conf file, find and uncomment the below line ( line no : 50 ) .
pop3_uidl_format = %08Xu%08Xv
Step 13 » Restart dovecot service.
[root@mail ~]# systemctl restart dovecot
Step 14 » Add firewall rules to allow 110,143,993 and 995.
[root@mail ~]# firewall-cmd --permanent --add-port=110/tcp
[root@mail ~]# firewall-cmd --permanent --add-service=pop3s
[root@mail ~]# firewall-cmd --permanent --add-port=143/tcp
[root@mail ~]# firewall-cmd --permanent --add-service=imaps
[root@mail ~]# firewall-cmd --reload

Check the connectivity for the ports 110,143,993 and 995 using telnet.

User creation

Now create user for testing .
Step 15 » Create user with /sbin/nologin shell to restrict login access.
[root@mail ~]# useradd -m john -s /sbin/nologin
[root@mail ~]# passwd john

Mail server is ready now, Configure user in your mail client and test send/receive.
Setup mail server on centos 7

Also see :
» Setup mail server on ubuntu 14.04
» Setup mail server on centos 6
All the best.


  1. This is my second time setting up a Linux email server. Following the directions in your tutorial for setting up an email server in CentOS 6, I was able to set up a working email server on CentOS 7. After realizing that you made a tutorial specifically for CentOS 7, I decided to try it out on a fresh system. I’m having some troubles though…

    If I’m reading it right, according to this tutorial, the only files in /etc/postfix/ssl in the end are: server.key,, server.csr, server.crt

    However, the edits to /etc/postfix/ make reference to the following in /etc/postfix/ssl which are not present: smtpd.key, smtpd.crt, cacert.pem

    postfix is failing to send email with errors in /var/log/maillog like:

    warning: cannot get RSA certificate from file /etc/postfix/ssl/smtpd.crt: disabling TLS support
    warning: TLS library problem: 11134:error:02001002:system library:fopen:No such file or directory:bss_file.c:398:fopen(‘/etc/postfix/ssl/smtpd.crt’,’r’):


    cannot load Certificate Authority data: disabling TLS support
    warning: TLS library problem: 8846:error:02001002:system library:fopen:No such file or directory:bss_file.c:169:fopen(‘/etc/postfix/ssl/cacert.pem’,’r’):

    I suppose I can rename all of the “server” files to “smtpd” files, but then I’m still missing cacert.pem. Am I missing a step?

  2. Fantastic article; right level of depth and explanation. I am new to setting up mail servers on linux, and this article was incredibly helpful. Now have a working mail server for JIRA to use; many thanks!

  3. Very clear and systematic instructions, and I think I have followed them correctly. Unfortunately I have not yet got postfix working. At least, I’m at the stage of trying to test it using telnet, and it keeps either rejecting the connection or closing the connection. I’m stumped. It’s either:

    $ telnet 587
    telnet: connect to address Connection refused
    telnet: Unable to connect to remote host


    $ telnet 25
    Connected to
    Escape character is ‘^]’.
    Connection closed by foreign host.


    The result for 465 is the same as for 25. All three ports are open in the firewall (25, 465 and 587). I have no idea where to go from here. I suspect that I have missed or mistyped something while following the instructions above, but I have no ideas on how to troubleshoot it to find the issue.

    Any troubleshooting pointers?

  4. I cannot set up the connection with SSL/TLS instead of STARTTLS. It drop an error. When trying with STARTTLS setting up the account on Mozilla Thunderbird, it says the username and password are incorrect. Tried many times but could do nothing else.

  5. Can i setup Mail on Server using Amazon instance EC2 (Centos 7 already installed). I don’t have any domainm i just have elastic IP which is not really static IP or global IP.

  6. I just fount this “tutorial” and must say ,,,, useless, doesn’t work on my CentOS 7, can open webmail but whatever i do it seems to not sending email or receiving emails.
    Any suggestions ?

  7. Good evening,

    Please I followed all the configuration steps, but in the end I can not run my email server with SSL support / tls. What should I do?

    Answer me please I really need your help

  8. hello,

    very clear, thanks but i have a probleme with password user.
    Its not working, i test with mozzila thunderbird, and i have a erro for validating password.

    so, i change the password user with : passwd john
    but after the thunderbird have the error with the new password

    please help me….

  9. Hi team,

    Nice tutorial. But won’t you have to install bind and add mx records, PTR records and TXT records(contains SPF) so that you can send mails successfully to even Gmail email ID’s and do not get caught in the spam folder

    Would really appreciate if someone could help me with the same.


  10. I can send emails to other mail servers but if i try to send an email to my new mailserver i always get: “Recipient address rejected: User unknown in local recipient table”. Any ideas?

  11. I’ve done everything in the tutorial, but thunderbird fails to login saying that the credentials are wrong, even thought they aren’t. How can I fix this problem? Thanks

  12. Plaintext authentication disallowed on non-secure (SSL/TLS) connection error

    my steps:
    1. telnet 110 + enter
    devecot OK ready

    2. user jek or + enter

    error Plaintext authentication disallowed on non-secure (SSL/TLS) connection error

    Please help me

3 Trackbacks / Pingbacks

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