Noel Jones:
> > By default, Postfix sends address verification probe messages via the
> > same route as regular mail,
>
> Yes, but it also says:
>
> Probe messages are like normal mail, except that they are never
> delivered, deferred or bounced
> - and -
> Postfix assumes that an address is undeliverable when the nearest
> MTA for the address rejects the probe, regardless of the reason for
> rejection
This text needs to be updated. The old Postfix SMTP client behaved
as if smtp_mx_session_limit=1, that is, there was only one SMTP
session per delivery request (it tried to connect to each MX until
one responded, and then it would not try any of the other MXes).
Why is it better to skip the fallback relay and reply with "4XX"?
Wietse
