On Tue, May 23, 2023 at 10:27:19PM +0200, Tim Jackson via Exim-users wrote:
> On 23/05/2023 13:21, Sander Smeenk via Exim-users wrote:
>
> > I try to send a message to 'info@???', but Exim
> > unexpectedly changes that to 'info@???', based on
> > some DNS queries it seems?
>
> > | $ exim -f ssmeenk@??? -bt info@???
> > | info@???
>
> I'm definitely not an expert, but is this not expected behaviour based on
> RFC5321 section 5.1 [1]?
>
> "The lookup first attempts to locate an MX record associated with the
> name. If a CNAME record is found, the resulting name is processed as
> if it were the initial name."
Section 5.1 of RFC5321 is named as "Locating the Target Host", it describes
how sender should obtain a list of ip-addresses to connect using target
domain name. Note that ip address lives on the 3-d OSI level, and domain
name is on 5-th or higher, they are different entities. Section 5.1 does not
describe whether original domain name should be transformed during
name-to-address resolution sequence, to send intermediate or final alias
to relay.
IMHO, the best practice is to keep original domain name regardless of
aliases chain. I don't know was it regulated by some RFC or not.
Historically, Sendmail has another behaviour, it leads to problems with
virtualhosts for mail service providers.
I treat the change of target domain as Exim's bug and tried to reproduce it
for test alias chains, with no success. But it definitely triggers for
email.postcodeloterij.nl, that's intriguing.
--
Eugene Berdnikov
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