Thank you again, Gary. This is helpful. I find this hard to believe since the archive function works fine with other clients. But I will check this out.
Hi Gary,
in the meantime I can confirm that you are right. I moved my mailbox to another Exchange server and the archive function works great.
Thanks, Ron
So how do all these other apps manage this kind of black magic? It’s clearly not impossible!
Repeating my general summary from previously:
iOS
- Native mail app
“We got this” - Spark
“We got this” - Outlook
“We got this”
Desktop:
- Outlook.
“We got this” - Mailbird
“We got this” - Thunderbird (via OWL add-on)
“We got this” - eM Client
How do all of these apps manage to do it?! Outlook sort of makes sense – maybe. But the answer given is that it is entirely related to the server side settings. I don’t doubt at all that that’s a factor, but obviously there is more to it than this because I have confirmed personally with each of the apps mentioned above with the exact same exchange server (I have since added Thunderbird / OWL since my previous comment) that they manage this out of the box with no additional configuration needed.
It would be really great if eM Client considered how this is possible and implement some solution as these others have. Maybe, in the absence of an announced archive folder, they simply look for a folder called “archive” and treat it accordingly. Who knows! But each and every one of the apps above has found a way to make this work seamlessly with all the same server limitations that have stymied eM Client.
Please, eM Client, just make it so already 
@Gary aside from the approach described above (look for an existing folder called “archive” and use that if present, otherwise create such a folder – which may be what all the other clients are doing to make this work), another solution would be to allow users to simply map the folder they want to use.
Whatever the solution found, it really would be great to get something to work here. Not having this folder mapped means that, for users with more than one account, the Archive button and the Archive keyboard shortcut don’t work across all accounts, and the workaround I’ve been using (assign a custom keyboard shortcut to move emails to the Exchange Archive folder) is prone to accidental misuse and sending emails to the archive folder on the wrong account.