are you wanting notifications for every banned action immediately? You might end up regretting that, you should anticipate getting hundreds of them daily.

iRedMail does send out a daily report to the postmaster (which you can also do a forwarding to your external address if you specifically want it there) which contains a listing of all the blocked IP's

Hello there.
Any help hand in my question?
Thanks

Thanks but what is the steps to follow?

Yes, I will follow your suggestion and I will report back here the result.
Thanks and Best Regards,
Mike Kranidis

I think you may need to do it in each specific jail.
Example: /etc/fail2ban/jail.d/sshd.local

Well looking further to my problem, I focused to activate the email sending in the case of ban for an IP address in send jail.
I realized that the iredmail has its own configuration files inside the /etc/fail2ban/jail.d/ directory. The file that I need to possible modify is: sshd.local with content :
root@mail:~#  cat /etc/fail2ban/jail.d/sshd.local
[sshd]
enabled     = true
filter      = sshd
logpath     = /var/log/auth.log
action      = iptables-multiport[name=sshd, port="22", protocol=tcp]
              banned_db[name=sshd, port="22", protocol=tcp]

So I think in this stage I need to integrate or implement the related action that according to manual is:
%(action_mw)s

The question is how?
Please guide me.

Thanks and Best Regards.

Dear Mr. Huangbin,
first of all many thanks for your answer.
As you suggested to me I added to /etc/fail2ban/jail.d/sshd.local one last line with:
sendmail[name=sshd, sendername=root@... , dest=mikek@...]

and I restarted the fail2ban
systemctl reload fail2ban.service-fail2ban.service

I ensured that fail2ban is restarted by looking at his log: /var/log/fail2ban.log

Then from another external server, I did the a ssh connection with bad password till I see my servers ip banned in iredmail server.

Unfortunately no email was created (I saw the sendmail log:  /var/log/mail.log) and ofcourse I did not receive something...
Please tell me what I did wrong?

Thanks and Best Regards

Ok here is the related fail2ban files:

root@mail:/etc/fail2ban/jail.d# cat ./sshd.local
[sshd]
enabled     = true
filter      = sshd
logpath     = /var/log/auth.log
action      = iptables-multiport[name=sshd, port="22", protocol=tcp]
#action      = iptables-multiport[name=sshd, port="22", protocol=tcp]
              banned_db[name=sshd, port="22", protocol=tcp]
              sendmail[name=sshd, sendername=root@xxxx.xx, dest=mikek@xxxx.xx]

root@mail:/etc/fail2ban# cat jail.local
[DEFAULT]
# time is in seconds. 3600 = 1 hour, 86400 = 24 hours (1 day)
findtime    = 3600
bantime     = 86400
maxretry    = 2
ignoreip    = 127.0.0.1 127.0.0.0/8 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16

When I do the ssh connection with the mistake password input, I confirm that fail2ban has been banned the external server ip but looking at the /var/log/mail.log ( doing tail -f  /var/log/mail.log ) NOTHING SHOWS.

What do you think?

Thanks

that was a mistake, I paste a previous not correct snippet, anyway I recheck it and see:
root@mail:/etc/fail2ban/jail.d# cat sshd.local
[sshd]
enabled     = true
filter      = sshd
logpath     = /var/log/auth.log
action      = iptables-multiport[name=sshd, port="22", protocol=tcp]
#action      = iptables-multiport[name=sshd, port="22", protocol=tcp]
              banned_db[name=sshd, port="22", protocol=tcp]
              sendmail[name=sshd, sendername=root@xxxx.xx , dest=mikek@xxxx.xx]

Nothing change, I triggered an ssh block / banning, I saw that the fail2ban.log  tooks the ip ban action but looking at the mail.log  nothing was send  and nothing received to me email...

What else?
Thanks

Thanks a lot for your help. I will try to see what is possible wrong in my case. If I found something I will report it back here.

that's odd, it should effectively do the same thing, but I restart my services like this: /etc/init.d/fail2ban reload
But at least it is working

/etc/fail2ban/action.d/sendmail.conf

Check here for the sample text that fail2ban uses for the notification email, you can edit as desired