[eli]

You can even donate a domain or have your own "private" mailinator domain by simply pointing the MX record for a domain or subdomain you control to their server.

[chadrs]

I've always wondered why a site that blocks mailinator sites wouldn't just do an MX lookup on any domain you put in and check for mailinator redirects.

[eli]

How much effort are you willing to expend to fight users who insist on giving you a throwaway account?

[Groxx]

Probably because it's harder than /@mailinator.com$/i. And the determined will always succeed anyway, so why go to great lengths?