[Users] Can you tell if an email address is valid without sending an email

[David Niklas]

Hello,
I was thinking that I wanted to be certain that the email addresses I get
from people I spell right and that they are valid, but I can't think of a
way to determine this unless I actually send the address an email.
This has the draw back that I have to wait, sometimes 1 whole day before
I learn if the email was actually delivered.

Thanks, David