How to Use Multiple Signatures using Outlook
I highly recommend assigning a signature to all accounts in Outlook 2003 (with Word as the editor), Outlook 2007, and Outlook 2010. This will allow the signatures to change when you change the account.
If the account doesn’t need a signature, assign a blank signature to it. To do so, create a blank signature that contains 2 dashes ( — ) to use when you don’t want to use a signature. When no signature is assigned to an account the signature feature is completely removed from the message and changing accounts will not update the signature.
Outlook 2010 or Outlook 2013
Provided you have assigned a signature to the currently selected account, Outlook 2010 or 2013 will change the signature when you select a different account from the Account dropdown
To set the signatures for each account, go to File, Options, Mail, Signatures and create your signatures then assign one to each account in your profile.
Provided you have assigned a signature to the currently selected account, Outlook 2007 will change the signature when you select a different account from the Account dropdown
Go to Tools, Options, Mail format, Signatures to create new signatures and assign them to each account in your profile.