A little bit testing, error.log while try to connect:
recv() failed (111: Connection refused) while reading response from upstream, client: 19.177.26.18, server: 0.0.0.0:993, login: "user@domain.com", upstream: 2.3.4.5:143
19.177.26.18 - my ip
2.3.4.5 - backend IMAP server
What its can be? Backend server rejects connection?
recv() failed (111: Connection refused) while reading response from upstream, client: 19.177.26.18, server: 0.0.0.0:993, login: "user@domain.com", upstream: 2.3.4.5:143
19.177.26.18 - my ip
2.3.4.5 - backend IMAP server
What its can be? Backend server rejects connection?