On 11 April 2018 at 19:43, Jeremy Harris via Exim-users <exim-users@exim.org > 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-) -- Systems Administrator & Change Manager IT Services, University of York, Heslington, York YO10 5DD, UK Tel: +44-(0)1904-323811 Web: www.york.ac.uk/it-services Disclaimer: www.york.ac.uk/docs/disclaimer/email.htm -- ## List details at https://lists.exim.org/mailman/listinfo/exim-users ## Exim details at http://www.exim.org/ ## Please use the Wiki with this list - http://wiki.exim.org/