Strange New Registration behavior

[Panzer Max]

Hey guys,

I have been watching the Mail delivery failed: returning message to sender emails I get from members who have bad emails, and I noticed something very odd today.

In addition to the members with bad emails who are subscribed to threads (which I can now delete with ease, thanks to the tip from kh99 :up: ), I saw one message that I do not understand.

SMTP error from remote mail server after RCPT TO:<correodeesxxx@hotmail.com>:
host mx4.hotmail.com [65.55.92.152]: 550 Requested action not taken:
mailbox unavailable

I checked and the message that was trying to be sent was the Registration message:

Dear Esquizoide,

Thank you for registering at the SUBSIM Radio Room Forums. Before we can activate your account one last step must be taken to complete your registration.

Please note - you must complete this last step to become a registered member. You will only need to visit this URL once to activate your account.

To complete your registration, please visit this URL: etc

I checked and there is no registration for that member with that Gmail in my system.

BUT! There is a newly registered member with that name and an exact same hotmail address.

My question: can someone try to register a name with one email, and without ever completing the registration (because the email failed, obviously), can they register successfully the same name with a different email?

I do not see how: if I register with the name John and the email john@gmail.com, then the username John should be in my db as Unconfirmed, waiting on email usergroup, right? No one can register the same username John again, right? Different email or not, that username should not be available.

This is very odd, like some kind of spambot behavior, can anyone explain?