I am having a strange sendmail / form email script problem that I hope someone might be able to help with:

If I submit a form-to-email page with a recipient that is a very long email address (such as name@reallylongdomainname.com), the form script responds with an Internal Server Error, however, if the recipient is a short email address such as hitspot@hitspot.net it works just fine.

I have tested the above with several form-to-email scripts (NMS formail, Matt's formail, Nethermail etc) with the same results - so it's looks like it's a serverwide problem, on all of my servers.
I'm wondering if a recent cobalt patch could have caused this? Anyone have any ideas on what could cause this problem?

Thanks,
David Kiley

I found it. In case anyone else ever experiences this problem:
It was just that the domain of the long email account that was causing errors when set as recipient was setup on our local server, and was currently being hosted on a third party server. (The user is currently moving this domain). Therefore, sendmail looked locally when sending the form-to-email and responded with an error as the email account had not yet been setup locally.