Hi davidep,
I tested with 2 different clients:
- Thunderbird 45.7.0 on Ubuntu 14.04 LTS
- cross check on Server2012R2 with Outlook 2016
Both logfiles do not report any errors.
What I can see in /var/log/imap:
Jan 31 10:12:40 dc2 dovecot: imap-login: Login: user=schloegl@intern.org, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=31681, secured, session=</i15VWBHUgB/AAAB>
Jan 31 10:12:40 dc2 dovecot: imap-login: Login: user=schloegl@intern.org, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=31684, secured, session=<KWl5VWBHVgB/AAAB>
Jan 31 10:12:40 dc2 dovecot: imap(schloegl@intern.org): Disconnected: Logged out in=589 out=4280
Jan 31 10:12:40 dc2 dovecot: imap-login: Login: user=office@schloegl-software.at, method=PLAIN, rip=10.140.1.2, lip=10.140.1.6, mpid=31691, TLS, session=
Jan 31 10:12:50 dc2 dovecot: imap(schloegl@intern.org): Disconnected: Logged out in=589 out=4280
Jan 31 10:12:50 dc2 dovecot: imap-login: Login: user=schloegl@intern.org, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=31699, secured, session=<GP0fVmBHYAB/AAAB>
Jan 31 10:12:51 dc2 dovecot: imap-login: Login: user=schloegl@intern.org, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=31702, secured, session=<ulogVmBHZAB/AAAB>
Jan 31 10:12:51 dc2 dovecot: imap(schloegl@intern.org): Disconnected: Logged out in=589 out=4280
Jan 31 10:13:01 dc2 dovecot: imap(schloegl@intern.org): Disconnected: Logged out in=589 out=4280
Jan 31 10:13:01 dc2 dovecot: imap-login: Login: user=schloegl@intern.org, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=31721, secured, session=<ZbHGVmBHbAB/AAAB>
Jan 31 10:13:01 dc2 dovecot: imap-login: Login: user=schloegl@intern.org, method=PLAIN, rip=127.0.0.1, lip=127.0.0.1, mpid=31724, secured, session=<EAjHVmBHcAB/AAAB>
Jan 31 10:13:02 dc2 dovecot: imap(schloegl@intern.org): Disconnected: Logged out in=589 out=4280
and (during a client triggered download) /var/log/maillog:
Jan 31 10:23:21 dc2 dovecot: pop3-login: Login: user=, method=PLAIN, rip=10.140.1.2, lip=10.140.1.6, mpid=620, TLS, session=
Jan 31 10:23:21 dc2 dovecot: pop3(schloegl): Disconnected: Logged out top=0/0, retr=0/0, del=0/0, size=0
Jan 31 10:23:21 dc2 dovecot: pop3-login: Login: user=, method=PLAIN, rip=10.140.1.2, lip=10.140.1.6, mpid=628, TLS, session=
Jan 31 10:23:22 dc2 dovecot: pop3(schloegl): Disconnected: Logged out top=0/0, retr=0/0, del=0/0, size=0