Hi Massimo,

also Stunnel:http://smedley.id.au/downloads/stunnel-5.50-os2.zip

build often uses a lot of cpu it seems without a good reason
(e.g. just one connection or nothing)

In your [SECTION] part, specify the protocol, ie, for POP3S,
specify

protocol = pop3

I have removed this from my config which then went to using
50% cpu after about a day, it then ran out of memory with errors
such as :-

2020.02.04 09:16:12 LOG3[ui]: Connection rejected: create_client failed
2020.02.04 09:16:12 LOG3[ui]: pthread_create: Not enough memory (12)

Cheers