I think I've found a solution.
Change in /var/qmail/supervies/imap4/env/IMAP_CAPABILITY from:
IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA IDLE
to
IMAP4rev1 UIDPLUS CHILDREN NAMESPACE THREAD=ORDEREDSUBJECT THREAD=REFERENCES SORT QUOTA
same for IMAP_CAPABILITY_ORIG
I'm also testing wait_timeout=180 in my.cnf