Oops, I meant 123.123.123.72
Just a bit tired here in the morning.
But what I wanted to say is that Microsoft is a extremely large internet
corporation, actually the largest, I think they own most IP-adresses too, so
what they do need to scale well.
-Ursprungligt meddelande-
Från: owner-postfix-us...@postfix.org
[mailto:owner-postfix-us...@postfix.org] För Sebastian Nielsen
Skickat: den 15 februari 2016 10:53
Till: 'postfix users'
Ämne: SV: Can this sort of spam be easily and safely blocked in postfix
[signed]
Yes, there is a reason.
If they have a large amount of virtualized servers set up using wildcarding,
like:
*.123.123.123.in-addr.arpa IN PTR mailservers.office365.com
Its of course not possible to add the corresponding forward record, because
that would create a pretty large forward zone, especially if Microsoft does
this with a large amount of IP-adresses.
Dynamically assigning reverse/forward, like *.123.123.123.in-addr.arpa IN
PTR *.mailservers.office365.com, so a server like 72.123.123.123 has a PTR
of 72.mailservers.office365.com, would require specialised name server
software, same with the forward zone, if you don't want unneccesarly large
zones.
You could however check which ASN's microsoft has, and then whitelist these
in a rule file so these IPs will be let through without any spam checking.
(Be careful however, so you don't put the whitelist too early and let
through mails you don't want to let through at all)
-Ursprungligt meddelande-
Från: owner-postfix-us...@postfix.org
[mailto:owner-postfix-us...@postfix.org] För Karel
Skickat: den 15 februari 2016 10:19
Till: postfix users
Ämne: Re: Can this sort of spam be easily and safely blocked in postfix
> On 2016-02-14 18:34, Bill Cole wrote:
>
>> are there any legitimate (non-spam) senders, that would be blocked by
>> reject_unknown_client_hostname ?
>
> Do you consider Microsoft's Office365 to be "legitimate?"
>
> They send substantial non-spam, yet many of their output IPs have PTR
> addresses which yield addresses which do not resolve back to the
> original IPs.
sorry for keep dwelling on this, but is there any reason why a legitimate
sender (ie Microsoft) would not use corresponding IP -> hostname -> IP ?
Is there some technical limitation that prevents them from doing it?
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