On Sun, Aug 30, 2020 at 05:33:51PM -0400, Wietse Venema wrote:
> Well almost: it needs a custom SMTP client to avoid loop detection.
>
> /etc/postfix/master.cf:
> pickup unix .. .. .. .. .. pickup
> -o { content_filter = local-smtp:[localhost]:25 }
>
> local-smtp unix .. .. .. .. .. smtp
> -o { inet_interfaces = }
> -o { myhostname = localhost }
>
> Let me know if that does the job.
Looks about right, perhaps a final note that with this one MUST NOT then
use "simple" content filters that resubit mail back into Postfix via
sendmail(1) (i.e. ultimately pickup).
Another thing to keep in mind with trying to prevent address forgery, is
that it can break various ways in which messages are forwarded (via e.g.
procmail) or "Resent" (via mail user agents), e.g. "mutt" can "bounce"
(really resend) a message, but it is polite and adds "Resent-From"
headers.
Also vacation message envelope sender addresses should be the null
sender address to avoid loops (see also RFC3834).
--
Viktor.
