What you can do, however, is set the program to allow you to choose a signature when you compose a message. This adds a pull-down menu to your compose window, allowing you to easily choose any signature you enter via this panel. Again, this is something that we imagine Apple will address in a future version. That is, it is our guess that users will be able to attach signatures to accounts, meaning that each account will be able to have a default signature, basically eliminating the need to choose the signature at composition time. Rules - Mail's rules are not as robust or full featured as those in Outlook Express, but should get the job done for most users.
Rules are actions that are applied to messages based on some criteria that the user selects.
So, for example, if you play in a volleyball league and you want all messages pertaining to that league to automatically go into a designated folder, you can do that. Combined with automatically moving a message, Mail's rules allow you to set the color of a message, delete it, forward it, or play a sound. There are a number of options, all of which include looking for a string of text in a certain area. You can invoke a rule from text located in the From, To, CC, or Subject fields. You can also have Mail search the body of a message for a string of text.