Email Validation?

[hoihtah]

i'm creating a user self registration page, and wondered about all the different methods of validating an email address. (i'm also trying to study php, so if this is possible with php scripts, that'd be great.)

and please, i'm not trying to spam anyone, this is for my own website.
no self respecting anandtech member will do such thing.

now that i've gotten that out of the way,
so far, i can think of few options.

at base level,
i can check for
-illegal characters
-existance of "@" and "."
-valid domain suffix : .com, .org, .net and so on.

on a level above that, i can check for the domain.
and see if the domain is registered.
so if someone inputs, joesmith@mail.hoihtah.com...
i can take hoihtah.com and check for its registration.

while i was doing some research on this topic,
i came across a higher level validation.
where you can take an email address and see if it can actually receive an email.

how can you do this without actually sending an email?

this would help me out a great deal.

i think in the end the best method would be to send an email with validation/activation link to the address and have the user verify it.

but with that being the last resort, is there another method?

thanx in advance