From Outlook Help
From the main Outlook window, on the Tools menu, click Options, and then
click the Mail Format tab.
In the Compose in this message format list, click the message format that
you want to use the signature with.
Under Signature, click Signature, and then click New.
In the Enter a name for your new signature box, enter a name.
Under Choose how to create your signature, select the option you want. For
Help on an option, click the question mark , and then click the option.
Click Next.
In the Signature text box, type the text you want to include in the signature.
You can also paste text to this box from another document.
To change the paragraph or font format, select the text, click Font or
Paragraph, and then select the options you want. These options are not
available if you use plain text as your message format.
To add an electronic business card - vCard - to the signature, under vCard
options, select a vCard from the list, or click New vCard from Contact.
Once you've created the signature, you can insert it in all new messages, in
all messages you reply to or forward, or just in a specific message.
To automatically insert a signature in all new messages, or in all messages
you reply to or forward
From the main Microsoft Outlook window, on the Tools menu, click Options,
and then click the Mail Format tab.
In the Compose in this message format list, click the message format that
you want to use the signature with.
Under Signature, choose the signatures that you want to use for new messages
and for replies and forwards.
Cheers!
Pravin
Microsoft MVP