Postfix and Dovecot Configuration

Installation

1. hostnamectl set-hostname mail.<domain>.<tld>
2. yum -y install postfix dovecot

Postfix Configuration

1. Append the following to /etc/postfix/main.cf:

   1. myhostname = mail.<domain>.<tld>
   2. mydomain = <domain>.<tld>
   3. myorigin = $mydomain
   4. home_mailbox = mail/
   5. mynetworks = 127.0.0.0/8 <domain IP>
   6. inet_interfaces = all
   7. mydestination = $myhostname, localhost.$mydomain, localhost, $mydomain
   8. smtpd_sasl_type = dovecot
   9. smtpd_sasl_path = private/auth
   10. smtpd_sasl_local_domain =
   11. smtpd_sasl_security_options = noanonymous
   12. broken_sasl_auth_clients = yes
   13. smtpd_sasl_auth_enable = yes
   14. smtpd_recipient_restrictions = permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
   15. smtp_tls_security_level = may
   16. smtpd_tls_security_level = may
   17. smtp_tls_note_starttls_offer = yes
   18. smtpd_tls_loglevel = 1
   19. smtpd_tls_key_file = /etc/letsencrypt/live/<domain>.<tld>/privkey.pem
   20. smtpd_tls_cert_file = /etc/letsencrypt/live/<domain>.<tld>/fullchain.pem
   21. smtpd_tls_received_header = yes
   22. smtpd_tls_session_cache_timeout = 3600s
   23. smtpd_use_tls=yes
   24. tls_random_source = dev:/dev/urandom
   25. virtual_alias_domains = <domain>.<tld>
   26. virtual_alias_maps = hash:/etc/postfix/virtual

2. Find and uncomment the following lines in /etc/postfix/main.cf:

   1. #inet_interfaces = localhost
   2. #mydestination = $myhostname, localhost.$mydomain, localhost

3. Append the following lines to /etc/postfix/master.cf:

   1. submission inet n - n - - smtpd
   2. -o syslog_name=postfix/submission
   3. -o smtpd_sasl_auth_enable=yes
   4. -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject_unauth_destination
   5. -o milter_macro_daemon_name=ORIGINATING
   6. smtps inet n - n - - smtpd
   7. -o syslog_name=postfix/smtps
   8. -o smtpd_sasl_auth_enable=yes
   9. -o smtpd_recipient_restrictions=permit_sasl_authenticated,reject_unauth_destination
   10. -o milter_macro_daemon_name=ORIGINATING

4. Make sure that the following is present in /etc/postfix/main.cf:

   1. alias_maps = hash:/etc/aliases

5. Edit and add the desired email address to /etc/postfix/virtual such as the following:

   1. info@<domain>.<tld> admin
   2. webmaster@<domain>.<tld> admin

6. Create a map database: postmap /etc/postfix/virtual

Dovecot Configuration

1. Find and modify the following lines in /etc/dovecot/conf.d/10-master.conf:

   1. # Postfix smtp-auth
   2. unix_listener /var/spool/postfix/private/auth {
   3. mode = 0660
   4. user = postfix
   5. group = postfix
   6. }

2. Find and modify the following lines in /etc/dovecot/conf.d/10-auth.conf:

   1. auth_mechanisms = plain login

3. Find and modify the following lines in /etc/dovecot/conf.d/10-mail.conf:

   1. mail_location = maildir:~/mail

4. Find and modify the following lines in /etc/dovecot/conf.d/20-pop3.conf:

   1. pop3_uidl_format = %08Xu%08Xv

5. Find and modify the following lines in /etc/dovecot/conf.d/10-ssl.conf:

   1. ssl_cert = </etc/letsencrypt/live/<domain>.<tld>/fullchain.pem
   2. ssl_key = </etc/letsencrypt/live/<domain>.<tld>/privkey.pem

Restart and Enable Services

1. systemctl restart postfix
2. systemctl enable postfix
3. systemctl restart dovecot
4. systemctl enable dovecot

Open Firewall Ports

1. firewall-cmd --permanent --add-service=smtp
2. firewall-cmd --permanent --add-port=587/tcp
3. firewall-cmd --permanent --add-port=465/tcp
4. firewall-cmd --permanent --add-port=110/tcp
5. firewall-cmd --permanent --add-service=pop3s
6. firewall-cmd --permanent --add-port=143/tcp
7. firewall-cmd --permanent --add-service=imaps
8. firewall-cmd --reload

Configure DNS

1. Add an A record for the mail server:

   1. name = mail.<domain>.<tld>`
   2. IP = <mail server IP>

2. Add an MX record:

   1. Hostname = mail.<domain>.<tld>
   2. Priority = 5

3. Add the following TXT records:

   1. Name = @
   2. Text = "v=spf1 ip4:<domain IP> ~all"
   4. Name = _dmarc.<domain>.<tld>
   5. Text = v=DMARC1; p=none

4. Add PTR record for <domain>.<tld>

5. Finally, test your email at https://www.mail-tester.com/

Notes on Using Let's Encrypt for SSL

Make sure that Encryption is set to STARTTLS when configuring mail clients

References

1. Krizna Article
2. Ubuntu Postfix Alias Configuration