SP2 is installed, but has been since well before the problem arose.
The item is not arriving with the correct class either.
Thanks for the speedy response!
If the message is not arriving with the correct message class, the most likely explanation is that something has happened to one-off the form. I would suggest checking the design again to make sure the "send form definition" box is still unchecked.
If this is happening only to one user, then clearing the forms cache would be a good idea.

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Sue Mosher, Outlook MVP
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> SP2 is installed, but has been since well before the problem arose.
> The item is not arriving with the correct class either.
[quoted text clipped - 12 lines]
> I am not sending form definition with the email. What has caused this
> to change? the form itself has not changed for months!