IMAP operations get stuck and never time out

Expected behavior

1. IMAP operations should work
2. If IMAP operations are having network issues, they should time out in a reasonable time

Actual behavior

Sometimes when I sync the inbox and when I send mail the operations get stuck. Inbox sync seems to eventually time out, although this can take many minutes and very rarely I believe this takes hours. Mail sending is much more prone to not timing out at all, I've just had it sit there trying to send a message for 2.5 hours. The issue is obviously more severe with sending email as my recipient has not received what may well be an important message.

I am running Dovecot on the server end with STARTTLS. I configured Samsung's email client to talk to the same server and it has no network issues - when K-9 gets stuck I open Samsung's email client and it works. I've never had Samsung's client get stuck since I started using it in parallel with K-9 some weeks ago.

Steps to reproduce

1. Pull down to refresh the inbox

OR

1. Compose an email
2. Click send

Environment

K-9 Mail version: 5.203

Android version: 6.0.1

Account type (IMAP, POP3, WebDAV/Exchange): IMAP (Dovecot) with STARTTLS

No source file or test is named. Start by reproducing the issue during inbox refresh and mail sending against Dovecot with STARTTLS, then trace the IMAP operations that remain stuck. Done means affected operations time out in a reasonable period instead of waiting for many minutes or hours.