A new appli has just been released.
It is called Mail Alert
It provides alerts for your email account (IMAP / POP) based on From and Subject values.
Here is the description :
Create warnings for incoming emails, according to rules / filters based on FROM/SUBJECT values.
IMAP (gmail, aol) and POP (hotmail, yahoo) are availables.
!! Need to be enabled on the email provider website !!
Still in development, fully free, thanks for your feedbacks
I tested it, it works nicely