Peter Wienemann via Postfix-users:
> Hi Viktor,
>
> On 2024-01-02 18:13:22 +0100, Viktor Dukhovni via Postfix-users wrote:
> > That said, indeed the documentation is not explicit on this point, one
> > has to read "between the lines". If your technical writing skills are
> > adequate, perhaps you could suggest some concise and clear text
> > explaining the semantics.
> >
> > This would need to be added to smtp(8), transport(5) and postconf(5),
> > with multiple affected parameters in the last case.
>
> here are my suggestions (I hope I provided enough existing context to
> make it clear where to insert the new text):
>
> smtp(8):
> ------------------------------------------------------------------------
> The Postfix SMTP+LMTP client supports multiple destinations separated
> by comma or whitespace (Postfix 3.5 and later). Delivery is tried in the
> specified order. For each individual destination the delivery rules of
> RFC 5321, Section 5.1 are applied.
> ------------------------------------------------------------------------
Unfortunately this says that RFC 5321 applies to LMTP deliveries,
and it ignores the possibility that SRV record lookups have been
enabled. I will keep the text that delivery is tried in the specified
order.
> transport(5):
> ------------------------------------------------------------------------
> This tries to deliver to bar.example (following the rules of RFC 5321,
> Section 5.1) before trying to deliver to foo.example.
> ------------------------------------------------------------------------
Here I think that the original text is more clear than the updated
text, which again implies that RFC 5321 applies to LMTP, and ignores
the possibility of SRV record lookups or [] MX overrides.
Clearly, it is not desirable to enumerate all the SMTP client's
email delivery strategies here. Those strategies are orthogonal to
the issue of multiple destinations, and they do not belong here.
> postconf(5):
> ------------------------------------------------------------------------
> Multiple destinations are supported in Postfix 3.5 and later. In this
> case delivery is tried in the specified order. For each individual
> destination the rules of RFC 5321, Section 5.1 are applied.
> ------------------------------------------------------------------------
Same problem. The text "delivery is tried in the specified order"
is correct, the thext that follows is incomplete or misleading.
> What I do not like about the above suggestions is the fact that the MX
> lookup part of RFC 5321 is skipped if the [] notation is used. Thus
> strictly speaking the rules of RFC 5321 are only partially followed in
> that case. But since the user explicitly requested Postfix to skip MX
> lookup in those cases, I hope that the above additions introduce more
> clarity than confusion.
There are many cases where MX lookup is not desirable. The most
common cases are the submiossion submoissions/smtps services; the
less common case is SRV lookups.
Wietse
> Of course it would be even better to explain the algorithm described in
> RFC 5321 with a few words directly in the Postfix documentation rather
> than refer to the RFC, but this would be really tough to achieve.
>
> Best regards,
>
> Peter
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