[Mailman-Users] Users complain, they don't receive mails from the list

Mark Sapiro mark at msapiro.net
Mon Jan 25 20:00:51 EST 2016

On 01/25/2016 04:27 PM, Sascha Rissel wrote:
> One thing regarding the Reverse DNS entry:
> How can it be necessary, to set up this record? Just imagine a server,
> where multiple domains are hosted, but the server only has one IP.
> If the ISPs really require rDNS entries, which suit to the mail originating
> domain, one would always need a 1:1 mapping of IP and domain, preventing
> multiple domains on a one-IP server, isn't it?

No. It doesn't matter how many From: or SMTP MAIL FROM domains the
server supports. the crucial things are:

The IP address of the server has an rDNS PTR record pointing to a name.
That name has an A record with the same IP address and that name is the
name with which the MTA identifies itself in SMTP HELO or EHLO.

In addition, web.de and lots of other ISPs require that the name itself
not be a generic looking name, and some go so far as to not like IP
addresses that are in a netblock used by an ISP for 'home' connections.
On this latter point I run an MTA on msapiro.net which at one time was
on a 'home' DSL connection with fixed IP with rDNS to msapiro.net, but
in spite of this proper configuration with a non-generic domain, I would
occasionally get flagged by Microsoft for "bot like behavior", the only
plausible reason for which is the IP was in a range used by the DSL
provider for 'home use'

Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan

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