--$  perl -MEmail::Valid
printf "%s\n",(Email::Valid->address("peter\@berghold.net")?"Yes":"no");
 
Yes
--$  perl -MEmail::Valid
printf "%s\n",(Email::Valid->address("peter@yuckster.com")?"Yes":"no");
 
 
no
--$  host yuckster.com
yuckster.com has address 216.21.229.209
--$  host -tany yuckster.com
yuckster.com name server dns21.register.com.
yuckster.com name server dns22.register.com.
yuckster.com has address 216.21.229.209