:-) Valaszt (meg) nem kaptam, de gyanitom, hogy mar nem is fogok, azonban az elkuldott levelet nyilvanosan is vallalni merem (az esetleges grammar issue-kkal egyutt), ime:
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Dear Mr Klensin,
I've read RFC5321 you have written, and I need your help to some clarification.
There's a free email provider (@citromail.hu) that uses an unusual smtp level check
againt spammers: it checks whether the domainname part of the email has a valid MX
record or not, and if not, it rejects the smtp session even if the domainname has a
valid A record.
There's a debate whether this check is RFC compliant or not, and I thought I would ask
your opinion about the matter since it's your RFC :-)
According to RFC 5321 (http://tools.ietf.org/html/rfc5321) 5.1 section (Locating the
target host):
The lookup first attempts to locate an MX record associated with the
name. If a CNAME record is found, the resulting name is processed as
if it were the initial name. If a non-existent domain error is
returned, this situation MUST be reported as an error. If a
temporary error is returned, the message MUST be queued and retried
later (see Section 4.5.4.1). If an empty list of MXs is returned,
the address is treated as if it was associated with an implicit MX
RR, with a preference of 0, pointing to that host. If MX records are
present, but none of them are usable, or the implicit MX is unusable,
this situation MUST be reported as an error.
Let's say I want to send an email and provide apache @ lithium.aaa.fu in
the MAIL FROM stage. The host 'lithium.aaa.fu' has no MX record, but has
a valid A record.
The paragraph above tells me that it's perfectly fine, and the receiving smtp
should not reject the smtp session because of the absense of the MX record.
So I would like to hear you opinion about the matter whether I am right or wrong.
Thank you in advance,
xxxxx
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