We've recently migrated from in house Exchange to Exchange online. My email client is Outlook 2010. This went fine, however removing the old account was tricky (you cannot remove a primary account, even if you are no longer using it).
I removed all mail profiles and re-added my Exchange Online profile. This has worked OK, and I can see all my emails, however I get a warning when I launch Outlook, warning that I am using a temporary mailbox. In addition, using this online mailbox is a slow and a bit laggy, as it's loading messages from the internet each time.
My local .ost file now is only 265KB (as all emails in cloud). I have a .pst which I want to import (~4GB in size) so that I have a cached local copy of emails. However, each time I do the import it runs for around 45 mins, but my .ost does not grow in size at all - i.e. it is not importing the .pst into the .ost.
I don't want to have to pay for a third party converter or anything, so there is there something fundamental I am overlooking here? Much obliged in advance.
Edit: the message I get when I launch my Outlook is: 'Your mailbox has been temporarily moved on Exchange Server. A temporary mailbox exists, but might not have all of your previous data.
You can connect to the temporary mailbox or work offline with all of your old data. If you choose to work with your old data, you cannot send or receive email messages.'