All the advice above is very good, but you're probably wondering "how do I check for an MX record in perl?" Well, it's pretty easy using Net::DNS. 
use Net::DNS;
my $resolver = Net::DNS::Resolver->new;
my $domain = "perlmonks.org";
my $query = $resolver->query($domain,"MX");
if ($query) {
    # They have an MX record, send the mail.
} elsif (gethostbyname($domain)) {
    # No MX record, but the host exists.  Send the
    # mail.
} else {
    # No host, and no MX.  No mail for you!
}

[download]
Update: If we don't find an MX record, we now check to see if that address exists using gethostbyname(), as it's valid to have hosts without MX records. Thanks to Kanji for spotting this.

Cheers,
Paul

In reply to Re: gethostbyname() and www prefix by pjf
in thread gethostbyname() and www prefix by Anonymous Monk

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