Sometimes you just want to test an email address to see if it’s valid, but you don’t actually want to send them an email.
Instead of sending an email with the subject of “Just testing”, it’s a simple programming task to check the validity of the address. You can check the syntax, if the domain name is valid and if the receiving mail server will accept mail for the address.
I did a search today and found several websites. One was broken, but this one worked perfectly:
Do you have any other good ones that should be mentioned?