System locking down ip via postfix & dovecot

OS type and version centos 7.9
Webmin version latest release
Virtualmin version latest release
Related packages fail2ban

Hi, I was wondering if anybody has come across this particular problem and can’t seem to find the reason, it may be something very silly that I’m missing but I thought I’d ask the question anyway.

I recently installed the system on a VPS in the cloud everything seems to work perfectly however when I set up a mailbox on a domain, I can access it only from the web GUI, for some reason when I put the credentials in for the connection for the mailbox into any mail, client fail2ban automatically blocks the IP address and it seems to alter between two programs, witches postfix and dovecot, I have tried deleting the user mailbox and resetting it up, checking the credentials 700 times are more and I continue to get the same outcome. Checked all DNS records. Everything seems perfect.

I also make sure that any mail client was properly configured, but when trying to connect to the mailbox the IP address is automatically banned in one of the two of the following dovecot or postfix

I have made sure that the IP has been white-listed in the system also, but for some reason, it continues with the same process of alternating between dovecot and postfix when trying to connect from any type of mail client.

Is this a common rookie set-up mistake or is there something else here at play that I’m overlooking?

Did you enter the user in the single user window or batch?
If you go to edit user, are they setup to use email?
Have you tried the usermin interface on port 2000?

Hi, it was a single-user set-up and has been every time, I’ve also changed the default port for users and admin from the default of 1000 and 2000 for security reasons.

The user also only has access to email and no other feature on the system.

Thank you for your reply I hope this information helps.

are you using the email clients auto configuration to add the email address to the client ?
have you altered the settings in fail2ban ?

I’m not sure if Postfix or Dovecot can ban IP addresses. You should check if you’re using the right username.

If your domain is, your VM admin user’s mailbox username is example. But all other emails users will have a format of

Check if you’re using the correct username.

they can not fail2ban does the banning

You should check the fail2ban log /var/log/fail2ban (it’ll be large so grep it down) and see what is triggering the block. Then check out /var/log/maillog to see what/where/when and you should be able to track this down to something obvious.

You can enable more debug in both postfix and dovecot but for something this fundamental it shouldn’t be necessary.

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