<firstname.lastname@example.org>: host mailin-02.mx.aol.com[22.214.171.124] said: 550 We would love to have gotten this email to email@example.com. But, your recipient never logged onto their free AIM Mail account. Please contact them and let them know that they're missing out on all the super features offered by AIM Mail. And by the way, they're also missing out on your email. Thanks. (in reply to RCPT TO command)What the heck? The message wasn't sent to firstname.lastname@example.org, so why are you telling me I should contact this non-existent person and tell them to use your stuff? (It's even better when you get these as a result of a joe job, as I did here.) Of course, the 550 is enough for me to know what's up, but how many typical users are going to understand that this means "Address does not exist"?
It's disappointing -- email used to be one thing that AOL did pretty well, as big ISPs go, but apparently the AIM marketing team has got its nose in now.
Hrm, actually, it's even stranger than that:
RCPT TO:<email@example.com> 550 MAILBOX NOT FOUNDSo there's some sort of special attribute in the above example that makes it undeliverable in a different way than a completely-nonexistent user -- and knowing what the special attribute is requires some knowledge of AOL mail internals. Lovely.