Hi Jenn, MonaP and whipping_boy,
The issue has been reported as solved and backlogged delivery queues have been cleared. For the detailed information, you can check it with the wiki page (http://community.office365.com/en-us/wikis/exchange/2740.aspx) or the Service Health Dashboard on the admin page. I suggest checking the mail delivery status on your side or your users’ side. If it doesn’t work, please post it back here. We will further monitor this thread about the progress on your side.
Thanks,
Monica Tong