[vultour]

My favourite is when the validation rejects anything with the service name in the email. I wonder whether it's to prevent somebody registering <anything>@<service> as a joke, or a really bad attempt at preventing <service>@mailinator.

[fencepost]

Well that would have caused me problems when Oracle started requiring registration for some form of Java downloads.

They haven't spammed that though, I don't think I've ever received any actual email to the "oracleblowsgoats" address. Probably keeps any sales droids from even bothering with me as well.

[shakna]

It's because it is a common spam action to use <site>@<free_email> when blasting out stuff. It's also common to try and use <something>@<site> in either/or the to/reply-to fields for spambots.

So, it is easier to blacklist it altogether.