diekuh Dear Diekuh,
In dovecot logs nothing special:
24.09.2020, 13:27:23 info imap(zozwigor@wigor.org)<29638><nhLoew2wMpmsFgH4>: Logged out in=40 out=1133 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
24.09.2020, 13:27:23 info imap-login: Login: user=zozwigor@wigor.org, method=PLAIN, rip=172.22.1.248, lip=172.22.1.250, mpid=29638
24.09.2020, 13:27:23 info imap(zozwigor@wigor.org)<29635><xhDmew2wLpmsFgH4>: Connection closed: Connection reset by peer (UID fetch running for 0.010 + waiting input for 0.001 secs, 584 B in + 85100+2419 B out, state=wait-input) in=699 out=86819 deleted=0 expunged=0 trashed=0 hdr_count=83 hdr_bytes=311 body_count=0 body_bytes=0
24.09.2020, 13:27:23 info imap-login: Login: user=zozwigor@wigor.org, method=PLAIN, rip=172.22.1.248, lip=172.22.1.250, mpid=29635
24.09.2020, 13:27:23 info imap(zozwigor@wigor.org)<29632><GCfiew2wKJmsFgH4>: Logged out in=99 out=1352 deleted=0 expunged=0 trashed=0 hdr_count=0 hdr_bytes=0 body_count=0 body_bytes=0
24.09.2020, 13:27:23 info imap-login: Login: user=zozwigor@wigor.org, method=PLAIN, rip=172.22.1.248, lip=172.22.1.250, mpid=29632
24.09.2020, 13:27:23 info imap(zozwigor@wigor.org)<29629><nNreew2wIpmsFgH4>: Connection closed: read(size=7448) failed: Connection reset by peer (UID fetch finished 0.013 secs ago) in=744 out=137781 deleted=0 expunged=0 trashed=0 hdr_count=100 hdr_bytes=370 body_count=0 body_bytes=0
24.09.2020, 13:27:22 info imap(zozwigor@wigor.org)<29627><zbTeew2wIJmsFgH4>: Logged out in=355 out=10331 deleted=0 expunged=0 trashed=0 hdr_count=6 hdr_bytes=37 body_count=0 body_bytes=0
24.09.2020, 13:27:22 info imap-login: Login: user=zozwigor@wigor.org, method=PLAIN, rip=172.22.1.248, lip=172.22.1.250, mpid=29629