Indeed - but it's less comfortable.
Onto that not all providers allow it.

Anyway I did not mean a confirmation code.
E.g. try to send an email from hotmail to
a non-existing address - it won't work.

On FICS, the FIDE chess server, your approval
is even bound to the home address given by your ISP.
They won't accept anonymous email services like yahoo.

www.web.de, one of the winning-award mail-services
sends your confirmation code with snail-mail, serious.