You forgot to mention which version of Outlook you're using.
Go into your Outbox, open the email, then close it. Then try to delete it.
Try working offline to delete it. Or open Outlook in safe mode: Start > Run >
outlook.exe /safe.
Post back to let me know how you made out.

Signature
Kathleen Orland - MVP Outlook
Outlook Tips: http://www.outlook-tips.net/
http://www.howto-outlook.com/
> I tried to send a 33Mb attachment with a Hotmail email from my Outlook
> program 2 days ago. I now know the maximum file size I can send via Hotmail
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>
> Cheers
Buzzjunkie - 12 Mar 2008 07:52 GMT
Hmmm... I tried opening Outlook (2003 with SP3) in safe mode - as well as
opening it with Working Offline selected and I still can't delete it. When I
try to open the message I still get the same dialog box: "Can't open this
Item. Outlook has already begun transmitting this message".
Any other ideas? I'll take a look at the links you supplied as well,
Kathleen.
Thanks.
> You forgot to mention which version of Outlook you're using.
>
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> >
> > Cheers
Buzzjunkie - 12 Mar 2008 08:26 GMT
Just to let you know, I've also restarted my PC and been completely
disconnected from the Internet and I still get the same results - no delete
and not being able to open the mail.
Buzzjunkie
> You forgot to mention which version of Outlook you're using.
>
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> >
> > Cheers
Brian Tillman - 12 Mar 2008 19:52 GMT
> Just to let you know, I've also restarted my PC and been completely
> disconnected from the Internet and I still get the same results - no
> delete and not being able to open the mail.
Method three in this is guaranteed to work:
http://www.howto-outlook.com/faq/messagestuckinoutbox.htm
If you're using a Hotmail account and the Outlook Connector, try deleting
the Hotmail account and recreating it.

Signature
Brian Tillman [MVP-Outlook]
>I tried to send a 33Mb attachment with a Hotmail email from my
>Outlook
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>
> Cheers
- Put Outlook in offline mode.
- Exit Outlook.
- Start Outlook.
- Delete the item in the Outbox folder.
- Put Outlook in online mode.