Outlook 365 Archive wont pull from Exchange server

Question

I have had multiple clients now that report having run out of space in their outlook account. I go to investigate and find that their Inbox, Sent, and/or Deleted items number in the thousands or tens of thousands. They don't want to delete those emails outright however when I try to run the Auto archive or even just a general Archive it only ever affects the emails up until the bottom of the mailbox in question where it says "there are more emails stored on the exchange server" or something to that affect. I click on that link and it loads in the rest of their inbox or whatever box I am in, and at the bottom it shows emails from multiple years previous, some back to 2016 or maybe even 2013.
When I hit the archive button and tell it to archive emails older than last year I kind of expect the emails from 2016 to go away instead of cluttering up the mailbox.
What am I missing here? The only way I have found to get those older emails behind the "Exchange server" link into the archive is to manually select them and then Move them to the Archive folder that I wanted them in the first place. If I try that with more than 50 emails at a time it all but crashes outlook, Its not a viable solution.
None of the solutions I've found online do anything, The COM addons, the Registry for the modified date, "set the retention for the folder" the option that no longer exists and the Admin portal no longer supports.
These are all on the Newest versions of Outlook through office 365.

Answer 1

Hi @Jacob Greenfield

There is a feature in Exchange Online (Office 365) named MRM (Messaging Records Management) which can be used to auto-archive emails which have reached a certain age from the primary mailbox to the archive mailbox.
For more detailed information about how it works, please refer to this link: Retention tags and retention policies in Exchange Online

By default all the mailboxes in a tenant would be assigned the Default MRM policy.
In the Default MRM policy there is a Default Policy Tag named Default 2 years move to archive, which automatically moves two year old messages from primary mailbox to archive mailbox.
However, if the mailbox doesn't have archive enabled, this tag won't do anything.
If you have just enabled archive for the clients, I suppose it may be the reason why it started to archive the old emails.

Besides the default policy, you may also create custom tags to decide how you would like to archive (or delete) the emails, added the tags to a custom MRM policy, then apply the policy to the mailboxes.

To create or manage the MRM policy and tags, you may use the classic Exchange admin center.

Once you apply the custom policy to a mailbox, it wouldn't process the emails instantly, instead would process it during a certain period.
To speed up this on certain mailboxes, you may connect to EXO powershell and run the following cmdlet:

Start-ManagedFolderAssistant -Identity <mailbox>  

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