On 12 Jun 2019, at 23.01, Cliff Hayes via dovecot <dovecot@dovecot.org> wrote:

Hello,

Some versions of Outlook will randomly rename the Junk folder to Junk Email.

This of course causes errors because Dovecot can no longer store junk.

I go in to Outlook for each user and add another Junk folder, so now they have Junk and Junk Email. This fix action lasts a while until Outlook decides to do it again.

According to https://www.imapwiki.org/SpecialUse Outlook might support RFC6154 SPECIAL-USE extension.

You can try setting special_use = \Junk for that junk folder.

Is there a way to tell Dovecot that if the Junk folder doesn't exist, try sending the email to Junk Email folder?

Dovecot does not do that. You must mean sieve script. You can add :create into your fileinto directive to make pigeonhole to create the folder if it does not exist.