[Dovecot] connectionlimit for pop3s?

Hello,

i have a user who is able to do pop3 on port 110 without problems and without limits. There are ~10 real users using same public IP. When switching to port 995 to use pop3s he is limited at connection count. Some people can reach pop3s-server successful, some getting a timeout. I cant find any errors or limits within my config or in my log, there are no differences between using plain text and using tls. Are there some special loglines to grep for at this situation? Maybe i missed some lines... At the moment i dont see server-side problems. Somebody knows some typical clientside problems when this problem occurs?

dovecot version is 1.2.11

Thanks, Hajo