I don't do C# but the VBA sample at http://www.outlookcode.com/codedetail.aspx?id=615 should show you how to do it, taking into account with editor the user has turned on.

Signature
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
> Anyway to insert the default signature (option->mail
> format->signatures->signature for new messages)
[quoted text clipped - 3 lines]
> Thanks
> Baron