Re: [exim-dev] MX record usage

I'm usually quite guarded in my responses, but...

On 30 Aug 2013, at 07:42, SirNoSkill <quandary82@???> wrote:
> According to
> http://www.webhostingtalk.com/showthread.php?t=958414
> exim doesn’t work without MX record.
>
> MX are not mandatory.
> As per RFC2821, if no MX is found, then the A record will be used.
>
> I was just writing to let you know that if this isn’t already fixed, it
> is a bug and should be fixed.
> And when I was attempting to send this message, I couldn't send, because
> the MX record is missing ...
> So it definitely isn't already fixed.
> So, Exim definitely is NOT conformant to RFC2821, and that should be
> fixed ASAP.
>
> See the error message:
> http://i.stack.imgur.com/X0TPJ.png

This is garbage. The error message is "relaying denied", which indicates nothing to do with MX records.

If Exim didn't "work without MX records" (and how you get to that from the thread you posted I'm at a loss to understand), then it wouldn't work in the millions of installations across Higher Education in the UK where it's used on a per-host, MX free basis. And the same in other sectors.

Of course it works without an MX. Here's an example - my domestic ISP provides me with a dynamic IP address that I map to a name. That name has no MX record (it has an A, an AAAA, and several CNAME records).

I can email directly to it using any of them:

--------> dnslookup router <--------
local_part=graeme domain=HOSTWITHNOMX.graemef.net
checking domains
cached no match for +local_domains
cached lookup data = NULL
cached no match for +mm_domains
cached lookup data = NULL
HOSTWITHNOMX.graemef.net in "! +local_domains : ! +mm_domains"? yes (end of list)
calling dnslookup router
dnslookup router called for graeme@???
domain = HOSTWITHNOMX.graemef.net
DNS lookup of HOSTWITHNOMX.graemef.net (MX) gave NO_DATA
returning DNS_NODATA
DNS lookup of HOSTWITHNOMX.graemef.net (AAAA) succeeded
__IPv6 ADDRESS__ in "0.0.0.0 : 127.0.0.0/8"? no (end of list)
DNS lookup of HOSTWITHNOMX.graemef.net (A) succeeded
__IPv4 ADDRESS__ in "0.0.0.0 : 127.0.0.0/8"? no (end of list)
fully qualified name = HOSTWITHNOMX.graemef.net
HOSTWITHNOMX.graemef.net __IPv6 ADDRESS__ mx=-1 sort=-978
HOSTWITHNOMX.graemef.net __IPv4 ADDRESS__ mx=-1 sort=-10
set transport remote_smtp
queued for remote_smtp transport: local_part = graeme
domain = HOSTWITHNOMX.graemef.net
errors_to=NULL
domain_data=NULL localpart_data=NULL
routed by dnslookup router
envelope to: graeme@???
transport: remote_smtp
host HOSTWITHNOMX.graemef.net [__IPv6 ADDRESS__]
host HOSTWITHNOMX.graemef.net [__IPv4 ADDRESS__]
graeme@???
router = dnslookup, transport = remote_smtp
host HOSTWITHNOMX.graemef.net [__IPv6 ADDRESS__]
host HOSTWITHNOMX.graemef.net [__IPv4 ADDRESS__]
search_tidyup called

The important bit there is:

DNS lookup of HOSTWITHNOMX.graemef.net (MX) gave NO_DATA

...yet it can still deliver. What you're saying it completely withut foundation.

Graeme