[Dovecot] Dovecot service not responding after about a week of uptime

[dovecot at pupat-ghestem.net]

Hello,

The issue of dovecot becoming unresponsive happened again but after 16 
days  instead of just 7 as before.

$uptime
09:53:01 up 16 days, 20:23,  1 user,  load average: 1.32, 1.01, 0.83

As advised before I tried to login through the IMAP port. Entering an 
incorrect password gets rejected right away. Entering a correct password 
just hangs indefinitely.

$openssl s_client -connect mail.pupat-ghestem.net:993 -quiet
depth=0 CN = mail.pupat-ghestem.net
verify error:num=20:unable to get local issuer certificate
verify return:1
depth=0 CN = mail.pupat-ghestem.net
verify error:num=27:certificate not trusted
verify return:1
depth=0 CN = mail.pupat-ghestem.net
verify error:num=21:unable to verify the first certificate
verify return:1
* OK [CAPABILITY IMAP4rev1 LITERAL+ SASL-IR LOGIN-REFERRALS ID ENABLE 
IDLE AUTH=PLAIN] Dovecot ready.
a1 LOGIN wrongUser wrongPassword
a1 NO [AUTHENTICATIONFAILED] Authentication failed.
a2 LOGIN goodUser goodPassword
[HANGS]

Jan 15 09:58:58 hebus dovecot: imap-login: Login: user=<goodUser>, 
method=PLAIN, rip=192.168.173.254, lip=192.168.173.2, mpid=29852, TLS, 
session=<dIO0g/7vQQDAqK3+>

After a restart of dovecot everything works fine:

systemctl restart dovecot.service



Thanks in advance.