Curious dovecot behavior with service_count = 0

[anon_user]

Hello,

I'm not experiencing this problem at all with service_count = 1
With service_count = 0, this is what I got randomly in my logs:

TLS: SSL_read() syscall failed: Connection reset by peer

To be successfully logged, the user have to initiate a new connection.

I primary thought about vsz_limit but I've put this value to 10GB (yes 
this is very overkill, that was just for the test) and that don't change 
anything.

I use the lastest version of dovecot.

Any ideas ?

Thanks.