algorithm - Determining the health/validity of an email address

Question

Routine maintenance on a website often involves verifying that links are valid, flagging bad ones, etc.

I know how to match email addresses via a script (especially in the context of a web page where they'd be in mailto: links). My question is how would I verify they're OK without spamming the address?

Stripping-off the domain and verifying it's listening on port 25 is a partial answer, but doesn't handle verifying the username/alias.

Is there a way to add this to my maintenance scripts for websites I manage?

I don't really care what language it's written in, so long as it works :)

Answer 1

SMTP used to have a 'VRFY' command, which asked the server if it believed the username was valid. Everyone turns that off now, to prevent spamming.

It also used to be possible to start sending an email, "MAIL FROM: ...", "RCPT TO: ...", and the receiving server would let you know right after the RCPT TO if the address wasn't any good. That doesn't work anymore, either.

This is a long winded way of saying, "No, I don't think there is a way to do that, without actually sending an email."