One of my users tried to send an email to 4000 mostly internal recipients from Outlook 2010 Pro parallels on a Mac but it was stuck in the Outbox. I had her move it to Drafts and then log into OWA and send it from there. It won't send from OWA either and is now just sitting in the Drafts folder. There are no error messages. The only tooltip is a warning that the email will be sent to 4000 individuals. When she clicks Send, OWA and Outlook 2010 both behave as if it sent the email, but it's still sitting in her Drafts folder with "This message has not been sent" at the top.
Submission queues are at 0. All Exchange processes appear to be running fine. Other emails are sending/receiving without a problem.
Server: Exchange 2010 SP2
Client: OWA and Outlook 2010 (Parallels)
Any suggestions?