I understand that I can set $signature to a file name with my signature. Then all subsequent outgoing messages will have that signature appended. Or I can set $signature to something else or remove the file. Then all subsequent messages will not have a signature appended.
But what I want is to be able to decide, for each outgoing message: I want to append a signature to this message. Is there a way to do this? Perhaps I want a vim macro that will append the signature to the message currently being composed? Does anyone have a ready-made macro? Kai