Re: unavailable email question

"Rik Wasmus" a écrit dans le message de news:
op.t3jbbxfj5bnjuv@metallium.lan...
> On Tue, 18 Dec 2007 15:13:02 +0100, Jerry Stuckle
> wrote:
>> Rik Wasmus wrote:
>>> On Tue, 18 Dec 2007 13:35:13 +0100, Captain Paralytic
>>> wrote:
>>>
>>>> On 18 Dec, 12:26, "Rik Wasmus" wrote:
>>>>> You could set up a cron job testing for the following:
>>>>> - find the MX record for the domain
>>>>> - try a RCPT TO in a socket connection
>>>>> - flag emailaddres as unavailable on error
>>>>> - decide your logic wether to delete the emailaddres or recheck it
>>>>> (perhaps a limited number of times) later
>>>>>
>>>>> See the comments at:
>>>>>
>>>> More improtantly see the Notes:
>>>> Note: This function should not be used for the purposes of address
>>>> verification. Only the mailexchangers found in DNS are returned,
>>>> however, according to >> RFC 2821 when no mail exchangers are listed,
>>>> hostname itself should be used as the only mail exchanger with a
>>>> priority of 0.
>>> .. which you can add yourself in the code or as last item to the
>>> returned MX records if none exist/can be found. If you code with that
>>> fallback in mind, I see no reason why you couldn't(/shouldn't from a
>>> technical standpoint, load is something else) write a script that makes
>>> use of this function to validate an emailaddress. True, it cannot be
>>> done by this function _alone_, that's what IMHO this note is about.
>>
>> Because the check is not reliable. It is perfectly possible for the a
>> check like this to succeed but the mail still be bounced, for instance -
>> i.e. when the main mail server is just a mail proxy and passes the
>> message on to others to handle. In this case the proxy may accept
>> everything and later the "real" server can reject it.
>
> Hmm, true, hadn't thought about 'accept everything' proxies...
> --
> Rik Wasmus

This will anyway reduce the number of really undeliverable email as this is
actually the main problem. The opposite would be a harder problem (telling
is not available and in fact it is)....as we would delete such address and
the customer want to receive our newsletter.
Anyway we are aware that there is no magic way to know if an email is still
active or not but we may use the 2 solutions to check it (MX and also
analyse the returned emails).

Thank you