> Is it possible to customize the bounce messages and include an
> encapsulated html message for MIME-compliant clients? If yes, is
> there some reason why one should not do that? I'd like to make
> postfix bounce messages easier readable for the average user...
All Postfix features are documented. If it isn't documented then
it isn't supported.
Postfix bounce messages (structured per RFC 3462) preserve all the
MIME attributes of the original message. Other MTAs use home-grown
formats that will corrupt returned messages with content other than
plain ASCII text.
You can use Postfix bounce(5) templates to change the text that is
presented to the user. You can even include URLs if you want. And
if you make it longer than 1-2 lines, chances that anyone reads it
will drop to near-zero.
However, you're welcome to propose a way to include a text/html
alternative besides text/plain in the context of the RFC 3462
framework. In particular I wonder what the bounce(5) configuration
interface would look like.
Finally, I will definitely not support yet another home-grown return