Hi there!
I noticed very BIG and STRANGE error with Server-side sync - pop3 method, in my on-premise installation. It is just not working. Version info: 1612(8.2.2.112) (bd is same).
Few words about my installation:
I have own mail server in intranet, Kerio Connect (now by GFI). So, in CRM I creating new pop3 e-mail profile, with correct settings, and turning off SSL both for POP3 and SMTP. For my account choosing that newly created e-mail profile and started test. And... very well, no errors, status - "Succeful". And I got test email in my inbox.
But I see in debug log in Kerio MailServer, CRM trying to receive mail. I see commands:
AUTH
AUTH (NTLM)
user (me) logged in
STAT
RETR #### (number of mail)
...and oops! Connection to POP3 server 192.168.1.5 lost: connection closed by remote host. User mrrobot@corpevil.com.
[01/Dec/2017 23:09:51][4384] {pop3s} Session end
That ip - IP of my CRM server. So, CRM cannot receve mail, just closing session.
After few hours CRM sending to me brilliant message, exactly: