Your description doesn't cover the main issues that will determine the appropriate solution:
1) Target audience -- internal users, external recipients, or both
If only internal users:
2) All users get mail from with Outlook? What version(s)?
3) All users get mail from Exchange mailboxes? If so, do you have permission to publish a custom form to the Organizational Forms library.
If the answers to #2-3 are not all Yes, then an Outlook custom form is not a viable solution. I'd recommend looking at InfoPath 2007.

Signature
Sue Mosher, Outlook MVP
Author of Microsoft Outlook 2007 Programming:
Jumpstart for Power Users and Administrators
http://www.outlookcode.com/article.aspx?id=54
> There seem to be three options to create and send a form via Oultook 2007: -
> 1. Custom form pages
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> Thanks in advance!
> Lou
Louverril - 18 Apr 2008 10:56 GMT
Thanks very much Sue - I was leaning toward Infopath!
I've not used it before but it's looks like it has a lot more featuires than
I thought.
At the moment as far as I'm aware - I need to do some more checking - all of
the users will be internal. If they are not I suppose infopath is out of the
question?
Cheers
Lou
> Your description doesn't cover the main issues that will determine the appropriate solution:
>
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> > Thanks in advance!
> > Lou
Sue Mosher [MVP-Outlook] - 18 Apr 2008 12:54 GMT
There may be ways to expose a forms server externally so you can use Infopath with external users, but I'm just not sure about that.

Signature
Sue Mosher, Outlook MVP
Author of Microsoft Outlook 2007 Programming:
Jumpstart for Power Users and Administrators
http://www.outlookcode.com/article.aspx?id=54
> Thanks very much Sue - I was leaning toward Infopath!
>
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>> > Thanks in advance!
>> > Lou
Louverril - 18 Apr 2008 13:34 GMT
Thanks Sue.
> There may be ways to expose a forms server externally so you can use Infopath with external users, but I'm just not sure about that.
>
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> >> > Thanks in advance!
> >> > Lou