hey,
i just sent an email into the nirvana to check ...
i was wrong about the failure notice, it is not the targeted server but the email server you send the mail from, which in my case was
mailer-deamon@googlemail.com and in your case makes things easierm since you just need to check for that sender and the
pattern of the failure message which i believe is up to the email server and in my case looked like this