How does Gmail recognize email signatures (alternatively, “What's the best way to recognize email signatures?”)

Question

Gmail automatically greys text that looks like a signature. Anyone have any guesses how it does this? (I've noticed that it depends on the presence of the sender's name, but I think that's only part of the story).

I ask because I'm working on a web application that has an email interface, and I'd like to remove users' signatures before displaying the contents of their emails.

Answer 1

Email signatures are supposed to be started with two dashes, a space, and a newline. See Wikipedia and RFC-3676