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Posted by Jerry Stuckle on 12/29/07 03:24
mp- wrote:
> On Dec 28, 5:56 pm, Iván Sánchez Ortega <ivansanchez-...@rroba-
> escomposlinux.-.punto.-.org> wrote:
>> The Natural Philosopher wrote:
>>> take the domain part of their address and try looking for MX, then A
>>> records..and hope their ISP doesn't have a relay in the way..
>> ... And do a port scan on pop3.domain, and imap.domain, and do keep a
>> whitelist of known domains and servers (together with a manual way of
>> adding a domain+server to that whitelist).
>>
>> --
>> ----------------------------------
>> Iván Sánchez Ortega -ivansanchez-algarroba-escomposlinux-punto-org-
>>
>> Why was God able to create the universe in only seven days? Because he
>> didn't have an installed base to deal with.
>
>
>
> Doing a port scan on imap.domain.com, pop.domain.com, etc.. just seems
> like taking an educated guess as to what the IMAP/POP3 server name
> is.
>
> Does a DNS record exist describing the hostname for a particular
> domains IMAP/POP3 servers? It seems that the MX record is only for
> SMTP - which doesn't necessarily mean IMAP/POP3 is on that same
> machine.
>
No DNS record for IMAP/POP3 because it isn't used for mail transfer.
SMTP needs it so that one system can send to another system. But with
IMAP/POP3 the user is requesting mail. Entirely different process which
doesn't require special DNS records.
As others have said - try the MX record for the domain. If that doesn't
exist, try the A record. If that doesn't work, you're SOL.
And it will fail on a large number of systems. Many large ISP's and
some large hosting companies use different IMAP/POP3 servers to keep the
load down on a single server, for instance. And many large companies do
similar, also.
--
==================
Remove the "x" from my email address
Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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