Seems that there is a problem with drafts sync to Apple mail. After creating a mail draft this is not sync to Apple mail in case that the app is open. Closing and restarting the app the draft is synced immediately. Sure, the most simple solution would be to point the finger to Apple, but in this case I think it’s not unambiguous.
I’ve tested this and it works as expected. I assumed you meant when you create a draft in the web app though and that is what I tested.
Apple Mail doesn’t check via IMAP all that frequently which means a few minutes can pass before the draft is shown in Mail. Closing and restarting Mail will cause it to show the draft as Mail checks the server and all folders on start up.
It’s worth pointing out that behaviour for the Inbox is different as we support IMAP IDLE for the Inbox which means as mail arrives there (by whatever route) a notification is sent to Mail to tell it to download new messages.
Than you for testing and for reply Dave!
The problem occurred when creating a draft on iPhone/iPad. When a draft was created on Mac it appeared immediately on iOS devices, but:
In the previous macOS version the Draft folder in Mac Apple Mail was hidden and appeared only when a draft was created AND was synced. After the update to 10.15.5 the Draft folder is always on, even when no drafts exist and the sync with iOS devices (which have the Draft folder always on for ages) works without problem. Yes, it was an Apple issue!
Hmmm, I was wrong!
The Draft folder is NOT default in Apple Mac Mail. After restarting the computer is hidden again…!