Outlook 2011 for Mac Office 365 Migration issues

Cannot understand why I can't upload large folders of e-mails into Office 365.  I go into Outlook 2011, there are 2,000 e-mails in the local database.  I drag them up to a folder in Office 365 - it says it's synchronised pretty quickly.  I'm dubious, so I hit 'Send / Receive'.  It slowly pans through the e-mails until it's uploaded all 2,000.

Still sceptical, so I then check on webmail, and there are 2,000 e-mails in that folder, dating back to 2001.  All good so far.

The next day I log on, and there are 200 e-mails.  On webmail, and in Outlook.  Why?  Has anybody else seen this?  I've done it three times now.  Also, a bunch of read requests have been triggered.  Anyone else familiar with this situation?
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Vasil Michev (MVP)Commented:
Old emails are most likely moved to the archive folder, default retention policy in Exchange Online is "move everything older than 2 years to the archive". Also check for the size of the mailbox, they might have been moved to a different folder or even to a hidden one.

If possible, use Outlook on a Windows machine to perform this, the Mac version uses EWS to access the mailbox.

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TechdivisionAuthor Commented:
Thanks - looks like it had all gone into the archive folder.
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