On 2017.08.25. 18:20, Viktor Dukhovni wrote:
>
> Yes, but ...
>
>> relay_transport = smtp:backend
>
> On MX gateway hosts that receive inbound mail, use "relay:..." not
> "smtp:..." for your relay transport, and let outbound mail from
> your system use "smtp". This reduces contention between inbound
> and outbound traffic, in particular slow outbound mail will not
> delay inbound mail.
>
>> relay_domains = mydomain.com
>> sender_dependent_relayhost_maps =
>> inline:{prioritysender.com=smtpfast:backend }
>
> No, because sender_dependent_relayhost_maps (unsurprisingly) only
> changes the relayhost, not the transport. If your priority is by
> origin, and not by destination, you may have to use three Postfix
> instances, with low priority traffic shunted to the default slow
> instance, and high priority traffic to the fast instance, with the
> front end instance acting as a switch to separate the two flows.
>
> Ultimately Postfix transport selection and concurrency limits are
> (correctly) destination based, so to implement sender-dependent
> behaviour you need to split the flow by sender, which can only be
> done by handling off to another MTA (instance) with sender-dependent
> relay settings.
>
> You could use:
>
>
> http://www.postfix.org/postconf.5.html#sender_dependent_default_transport_maps
>
> but only when the destination domain is not a "relay" domain or
> similar, that is, only if mail for the destination in questin just
> goes whereever the MX records point with no transport overrides
> beyond (sender_dependent_default_transport_maps) which selects a
> sender dependent *default* transport.
>
I'm using permit_auth_destination and it does not play without
relay_domains.
well, looks like I found few solutions:
1. change transport using FILTER via check_sender_access in
smtpd_sender_restrictions - fine until there is no other filter action
2. alter nexthop with sender_dependent_relayhost_maps - require
additional address on the backend
As I understand concurrency limits will differ from ones on default
route in both cases.
IMO it may be useful to allow alter transport in
sender_dependent_relayhost_maps as well in future releases of postfix
