Outlook IMAP Inbox not Updating

I’ve recently found that creating sub-folders in the Inbox of an IMAP email account can inhibit the updating of the Inbox message list, despite the “Send/Receive” actions completing without error.

The details of the configuration are:

Outlook Version: 2016
Mail Server: Dovecot 1.2.9
Inbox location: /var/mail/<username>

When Inbox sub-folders are created, the are stored on the server in an “INBOX” subdirectory of the user’s mail directory (/home/<username>/mail/INBOX).

My theory is that this results in Outlook expecting to see new mail in /home/<username>/mail/INBOX instead of /var/mail/<username>.

In any case, moving the subdirectories to the root of the mailbox instead of within the Inbox seems to have solved the problem.