There are situations when you want to switch to another signature while writing a message. For example, your formal signature with business contact information may be the one you assign to your work e-mail for corresponding with most colleagues. When you are just e-mailing co-workers that know you well, you may want to use a plainer signature. When you correspond with a new customer, you may want to use something fancy.
Switching to another signature in a message that you are composing is easy: Just click the arrow on the Signature button at the top of your message or right-click the signature itself and then choose another signature from the list (as we've shown in the picture).