I have a few users for some reason when sending messages the message is sent however, the message remains in their outbox. This happens sporadically. One month it happens and then four months later it repeats itself. I was finally able to recreate the problem sending some attachments. The attachments were 60k in size. The user sent the message to myself and I was able to receive it with it stuck in her outbox. I forwarded the message all around and had no problems receiving this but I was in another office. it is just the folks in her office having this issue.
I had the user to try this using OWA and we were able to recreate the problem. One other thing to note that when trying to move the message from the outbox the machine locked up. We went in OWA and tried this and we received an error that the message was moved access denied from the users mailbox with her logged on with her credentials.
I know this might sound like a network issue but I did a outlook.exe /rpcdiag and there were no failures. Also everything else is working fine as far as I could tell on the machine please help.