> On Nov 29, 2016, at 8:18 PM, troy_post...@piggo.com wrote:
>
> But for mail already sitting on the server here, what's the best way to
> forward (re-queue?) all of that to her user@isp_domain.com? There are
> thousands of emails.
Given that you know the envelope recipient, you need to re-inject this
back into the mailstream for delivery via the sendmail(1) command, and
carefully specify the new envelope recipient on the command-line, making
sure to not revive any other (header) recipients.
Use the user's old address as the envelope sender in order to avoid SPF
issues. So the minimum command to forward a single message file is:
/usr/sbin/sendmail -f "user@here" -i -- "user@there" < msgfile
However, depending on what headers your email system prepends, it may
be prudent to strip any locally added "Delivered-To:", "X-Original-To:"
and similar headers.
Don't send everything at once. Send a couple of test messages and
check with the user that they are arriving intact.
Even then send the mail slowly, don't flood the users mailbox, the
downstream MTA may object to excessive arrival rates for a single
user.
That said, the best approach is to give the user temporary IMAP
access, so that the user can download any missed email, and not
forward it all. Or provide access to a tarball with all the
messages, ... Forwarding can run into obstacles with DMARC,
anti-spam controls, ...
--
Viktor.
