[Dovecot] maximum number of channel in thunderbird

[Kakà]

Sometimes a customer of mine, receives from thunderbird the error 
"Maximum number of channel opens..." or something similar. I've tried to 
put this :

mail_max_userip_connections=100;
Into dovecot.conf but without results. The customers have 3 IMAP account 
on the server.

Can you please help me ?

  Hi, kako.