[Pkg-exim4-users] Use of primary_hostname with visiblename

Marc Haber mh+pkg-exim4-users at zugschlus.de
Wed Oct 18 16:22:00 UTC 2006

On Wed, Oct 18, 2006 at 11:16:27AM -0400, Bill Horne wrote:
> Marc Haber wrote:
> >Hi,
> >
> >On Wed, Oct 18, 2006 at 09:01:10AM -0400, Bill Horne wrote:
> >  
> >>Because I have been trading emails with a system that demands perfect
> >>forward/backward lookups on HELO info, I've changed the primary_hostname
> >>of my Exim4 installation. 
> >>
> >>I have Linux setup as billhorne.homelinux.org, but because that name
> >>doesn't match the MX record assigned to my IP address, another MTA is
> >>refusing to accept my mail. Ergo, I have forced Exim to use the A record
> >>assigned by my ISP.
> >>    
> >
> >A host checking that a message coming in from the MX host of the
> >domain is fundamentally broken. That host is going to miss a _lot_ of
> >mail.
> >  
> Sorry, I made a mistake: the MTA in question is checking the PTR record, 
> not the MX record. As I understand it, most MTA's check only for the 
> _existence_ of a PTR record, not whether it matches the A record, but 
> this one is rejecting emails if the A record doesn't match the PTR.

That's still fundamentally broken. Your MX points to an IP address,
and that IP address has a PTR record and the A record to that PTR
record's contents points back to the IP address.

That's perfectly fine. My setup is the same:

[1/500]mh at scyw00225:~$ host -t mx zugschlus.de
zugschlus.de mail is handled by 30 mailgate2.zugschlus.de.
zugschlus.de mail is handled by 10 mailgate.zugschlus.de.
zugschlus.de mail is handled by 20 q.bofh.de.
[2/501]mh at scyw00225:~$ host mailgate.zugschlus.de.
mailgate.zugschlus.de has address
[3/502]mh at scyw00225:~$ host domain name pointer torres.zugschlus.de.
[4/503]mh at scyw00225:~$ host torres.zugschlus.de.
torres.zugschlus.de has address
[5/504]mh at scyw00225:~$

> >In your case, I'd use your ISP's smarthost since a lot of hosts don't
> >accept messages delivered directly from residential DSL connections.
> >  
> My IP is in a fixed block, and is not marked portable, i.e., it does NOT 
> show in any of the RBL's as a "dynamic" IP. I won't use the smarthost, 
> because Speakeasy has asked its users not to point MTAs at their 
> smarthost.

Is there a single DSL provider in the US with even a remote clue?

>  Given that I have a fixed IP and a PTR record, I had thought I was in
>  compliance with the generally-accepted practice, but I'll take this
>  opportunity to ask if "A" and "PTR" records are supposed to match 
>  even though the domain name in my HELO pointed to the IP I was using.

I think that the PTR record should have a matching A record, but in
generall I wouldn't require that the host name pointed to by the MX
record matches the PTR record.

> This is, of course, a very common setup: I use dyndns.org to provide me 
> free DNS service, and my proprietary domain names (e.g., billhorne.com) 
> are forwarded to the billhorne.homelinux.org domain provided by dyndns.org.

Agreed. I think that your remote side is fundamentally broken. They
would reject mail from me as well.


Marc Haber         | "I don't trust Computers. They | Mailadresse im Header
Mannheim, Germany  |  lose things."    Winona Ryder | Fon: *49 621 72739834
Nordisch by Nature |  How to make an American Quilt | Fax: *49 621 72739835

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