I have a Mac (Yosamite 10.10.5 - can't upgrade OSX version due to necessary software compatibility) which since two days ago has started logging every single action it performs on the IMAP mail server.
It's always in the format
26-04-2018 mailserver.domain.tld <debug> Synchronize (OK)
but it logs this for every single IMAP and SMTP action - send, receive, check, synchronize etc leading to the Mail log becoming gigantic and eating all the disk space.
I can guarantee that Connection Doctor > Log Connection Activity is not checked.
Does anyone have any idea what could be causing this constant logging of debug-level messages and how I can prevent it?