Slow IMAP connection with Comodo Firewall


I am trying Comodo Firewall and experience a strange behavior. It seems that the connection to a IMAP mailserver in my netwerk slows down enormous. After the connection is established everything is fine. It occurs with several mail clients and the problem disapears when I shut down the Comodo Firewall.

I tried this:
but that doesn’t help me.

Can you advise me what to do?