On Thu, Jan 14, 2010 at 01:11:17AM +0100, Hector Martin wrote:
> What I want to do is rewrite the envelope sender such that it appears to
> come from the left hand side of the alias map file, so a mail from
> b...@gmail.com to f...@example.com would turn into a mail from
> f...@example.com to foo...@gmail.com. Is there a way of doing this in
> Postfix?
Perhaps with an SRS milter, or similar content filter, assuming these
take extreme caution to avoid loops (never rewrite "<>" to a non empty
return path) and provide appropriate means for bounces to come back to
the original sender in most cases.
Nothing built-in, because supporting the return path requires non-trivial
state.
To support this in Postfix itself, one needs an address class for domains
handled in this way, and a special delivery agent that processes mail
for such domains.
The delivery agent would:
- Securely handle return-path transformations to allow back-propagation
of bounces.
- Carefully replace the sender address before forwarding messages.
Deal with DSN notification attributes, ...
The SMTP server would perhaps need to be able to validate authenticated
bounces to return paths generated by the redirect delivery agent.
Alternatively, since bounces don't bounce, one could consider receiving
mail to any address in such a domain, provided the sender is "<>".
You would still be able to alias selective users in normal domains, but
would do indirectly. Hypothetically:
main.cf:
indexed = ${default_database_type}/${config_directory}/
redirect_transport = redirect
redirect_domains = redirect.example.com
redirect_maps = ${indexed}redirect_maps
virtual_alias_maps:
u...@inside.example.com uni...@redirect.example.com
redirect_maps:
uni...@redirect.example.com u...@outside.example.net
You would still need to spam filter very well before forwarding
significant volumes of email, otherwise the reputation of your forwarding
systems will be poor, and they experience delivery issues despite
(double negative) lack of SPF non-compliance.
No such delivery agent has been written, or address class implemented,
these are just random thoughts on what this would look like if supported
directly, rather than in content_filter or milter.
--
Viktor.
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