On Wed, January 19, 2022 13:29, Wietse Venema wrote:
> James B. Byrne:
>
>
> For me, alt4.gmail-smtp-in.l.google.com does not resolve to
> 66.102.1.27, but instead to 142.250.153.26 (and some IPv6).
>
> Wietse
>
Repeated dns lookups of alt4.gmail-smtp-in.l.google.com return a different ip4
address for each query. I infer that google.com uses a round-robin set of A
records for that domain; and likely multiple MX hosts for sending.
Although the returns I get seem to be in the 64.233.184 netblock and usually
one of either 64.233.184.26 or 64.233.184.27, neither of which are a PRT record
to alt4.gmail-smtp-in.l.google.com. Neither does 142.250.153.26 point back to
alt4.gmail-smtp-in.l.google.com for that matter.
However that may be, google's dns records are outside my span of control. I
still do not understand why a DSN delay message cannot be sent back to the
origin. Has google configured their mail servers to prevent this? Are the
bounces supposed to be sent somewhere else (aspmx.l.google.com.)? Do I have
some sort of configuration error?
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