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Pinging a domain name is not an especially good indicator - there are a number of scenarios where a domain name will not respond to pings, but can accept mail.

Firewall set up to allow incoming traffic on TCP 25 (the port for SMTP) but block ICMP traffic (e.g. pings). Many firewalls block ICMP traffic by default.
Yo-yo server - because of the way sending mail servers keep retrying mail, the receiving end only needs to be alive 50% of the time to offer a fairly reliable mail service. So even if the server is down (and not responding to pings), you could still send e-mail to it.
A DNS MX record exists for a host but no A/CNAME record. Given the following DNS configuration:
```
example.org.      MX 10    mail.example.org.
mail.example.org. A        10.10.10.1.
www.example.org.  A        10.10.10.2.
```
You will end up with a situation where mail.example.org and www.example.org will accept pings, but example.org will not accept pings (unknown host), yet addresses like joe@example.org can still be received.

So don't ping the domain. Use a Perl module like Net::DNS::Resolver to look up an MX record for the host; if there is no MX record, then look for an A/AAAA/CNAME record; if you've still not found a matching DNS entry, then the domain name probably can't receive mail.

use Net::DNS::Resolver;

my $domain = 'example.com';
my $dns    = Net::DNS::Resolver->new;
my $valid  = $dns->query($domain, 'MX')
             || gethostbyname($domain);
printf(
   "You could %s send mail to %s.\n",
   ($valid ? "maybe" : "not"),
   $domain,
   );
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In reply to Re: Creating a web application in Perl by tobyink
in thread Creating a web application in Perl by Anonymous Monk

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