WordMail does not include an Insert | Signature command like the regular
Outlook editor. If you want to be able to insert a signature into a WordMail
message manually, you can create an AutoText entry for each signature. You
can then insert them with the Insert | AutoText command.

Or, create multiple signatures the normal way (Tools | Options | Mail
Format) and make one the default. If you want to use a different signature
for the current message, right-click the signature that Outlook inserted
automatically. From the pop-up menu, select either the name of the signature
you want to use or E-mail Signature to create a new one. I personally prefer
this technique. This is also the technique you need to use if you want
Outlook 2003 to automatically change your signature when you switch accounts
on an unsent message.