The problem is that it is not necessarily good and wanted for forwarder
to tell sender what address the email is being forwarded to - there are
various privacy issues involved. Not to mention that just answering with
address like that will be used by spammers.
Now 551 error code is in fact supported by many systems, but it is
primarily for [temporary] forwarding in cases like when user changes his
email address. That case can be compared to what you change your phone
number and for period of time phone company will answer with automated
message on old number saying what new phone number now is.
On Thu, 20 Jul 2006, Robert Millan wrote:
Another approach at solving the forwarding problem is using standard 551 code,
which eventualy (let's hope) every MTA will be able to interpret and act
accordingly without generating a bounce:
551: User not local; please try <foo(_at_)bar(_dot_)org>
There's a plugin for qpsmtpd (in their wiki) to activate this via ~/.redirect.
The next version of Exim (4.63) will have support for generating this code by
prepending the error message with "551 ".
For example, in /etc/aliases:
foo: :fail: 551 User not local; please try <foo(_at_)bar(_dot_)org>
Or, if you want to enable it via user dotfiles:
dot_redirect:
driver = redirect
check_local_user
require_files = $home/.redirect
verify_only
allow_fail
data = :fail: 551 User not local; please try <${readfile{$home/.redirect}{}}>
condition = ${if !exists {$home/.forward}}
I've setup an "echo" redirection gateway for testing purposes. It's in
<echo(_at_)aybabtu(_dot_)com>. Feel free to give it a try.
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