Post the file /etc/firewalld/zones/iredmail.xml and any others in that folder

/etc/firewalld/

firewalld.conf:

# firewalld config file

# default zone
# The default zone used if an empty zone string is used.
# Default: public
DefaultZone=iredmail

# Minimal mark
# Marks up to this minimum are free for use for example in the direct
# interface. If more free marks are needed, increase the minimum
# Default: 100
MinimalMark=100

# Clean up on exit
# If set to no or false the firewall configuration will not get cleaned up
# on exit or stop of firewalld
# Default: yes
CleanupOnExit=yes

# Lockdown
# If set to enabled, firewall changes with the D-Bus interface will be limited
# to applications that are listed in the lockdown whitelist.
# The lockdown whitelist file is lockdown-whitelist.xml
# Default: no
Lockdown=no

# IPv6_rpfilter
# Performs a reverse path filter test on a packet for IPv6. If a reply to the
# packet would be sent via the same interface that the packet arrived on, the
# packet will match and be accepted, otherwise dropped.
# The rp_filter for IPv4 is controlled using sysctl.
# Default: yes
IPv6_rpfilter=yes

*************************************
lockdown-whitelist.xml:

<?xml version="1.0" encoding="utf-8"?>
<whitelist>
  <command name="/usr/bin/python /usr/bin/firewall-config"/>
  <selinux context="system_u:system_r:NetworkManager_t:s0"/>
  <selinux context="system_u:system_r:virtd_t:s0-s0:c0.c1023"/>
  <user id="0"/>
</whitelist>

Please, where to write / change it to a new port?

Thank You, 7t3chguy!

I changed my SSH port on:

/usr/lib/firewalld/services/ssh.xml
/etc/firewalld/services/ssh.xml

and, as I said before changes are made to the file
/etc/ssh/sshd_config

systemctl restart firewalld
or/and
systemctl enable firewalld

Everything works fine!