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Re: current usage of AAAA implicit MX?

2008-04-05 13:14:28
On 2008-04-04 22:46:17 +0200, Arnt Gulbrandsen wrote:

Since data entry software matters and noone else has mentioned that 
area, I searched CPAN and found three modules to help verify email 
addresses in web forms etc., namely Mail::Verify, Net::validMX and 
Email::Valid. All three do MX/A lookups, none do AAAA lookups.

The first two are IPv4 only. They also check if there are A records for
the RHS of the MX records and return an error if they can't find any.
So they will also flag            IN MX   1
                              IN MX   10        IN AAAA 2001:db8:ffff::1       IN AAAA 2001:db8:ffff::2

as invalid. 

The third just checks if there is an MX record, but doesn't check the
contents in any way. So        IN MX   1 no-such-host.invalid.

will be reported as valid.

Neither behaviour really reflects the validity of a domain if there is
IPv6 connectivity (although the first makes some sense as a generic
test: Any domain reachable only via IPv6 can be considered unreachable
in practice now and at least for the next few years).


   _  | Peter J. Holzer    | It took a genius to create [TeX],
|_|_) | Sysadmin WSR       | and it takes a genius to maintain it.
| |   | hjp(_at_)hjp(_dot_)at         | That's not engineering, that's art.
__/   | |    -- David Kastrup in comp.text.tex

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