Will,
In that case, take a look at the mail headers. How to do this varies with mail application, but assuming Outlook,
1. Open the message
2. From the menu, select "View", then "Options..."
3. This will display the message options page:
4. The message header appears in the box at the bottom labeled "Internet Headers". They may be quite long.
Outlook Express is similar but not identical. If you're lucky enought not to be using an MS mail product at all, I can usually help with most of the common ones...
This will give us some clue as to where the message has got "stuck". You probably shouldn't post the header here due privacy issues, but if you would like me to take a look, feel free to PM them to me.
(The only way provided by Outlook to pass this information on is to Cut and Paste it somewhere.)