On 11 April 2018 at 19:43, Jeremy Harris via Exim-users <exim-users@???
> wrote:
> That would be incorrect per standards. The HELO name should identify
> the sending system.
>
Umm… Agreed, but what if this mysterious and obfuscated organisation has
multiple A records under different domain names pointing at the system Exim
is running on? Wouldn't it then be valid to use any of those in the
HELO/EHLO command? E.g.,
- a.example.com is an A record pointing at ww.xx.yy.zz
- b.example.net is an A record pointing at ww.xx.yy.zz
Wouldn't it then be permissible to use a.example.com in the HELO/EHLO when
sending from an "@a.example.com" address, but b.example.net when sending
from an "@b.example.net" address?
RFC 5321 section 4.1.1.1 states: "The argument clause contains the
fully-qualified domain name of the SMTP client, if one is available." which
both of the above examples would fit. (The RFC doesn't explicitly state it
has to be the rDNS name of the server, although one could argue the
following sentence — "In situations in which the SMTP client system does
not have a meaningful domain name (e.g., when its address is dynamically
allocated and no reverse mapping record is available), the client SHOULD
send an address literal" — might be taken to imply it.)
If it is the case that the primary host name of the server MUST be used,
I'm struggling to think of a use-case when Exim's helo_data could be used
validly; I'd (possibly incorrectly?) assume it was for the above type of
scenario. Is it instead, say, only for use when sending out from Exim
running on a server with multiple interfaces?
Cheers,
Mike B-)
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