From Jan Barnholt:
Allows you to select a different signature for your favorite eMail application each time you login or boot your computer and optionally after a customizable time-interval.
All signatures are kept in a single, plain text file (the 'database'), a random quote is chosen each time 'SignatureRandomizer' is launched. The program writes the new signature to a file called 'CurrentSignature.txt'.
Select this file as signature in your favored eMail application.