Title: Exim>=4.94 transports: tainted not permitted
Author: Fabian Groffen <email@example.com>
The Message Transfer Agent Exim disallows tainted variables in transport
configurations since version 4.94. Existing exim.conf configurations
in /etc/exim need to be reviewed for breakage prior to upgrading to
>=mail-mta/exim-4.94 to avoid error conditions at runtime.
Since the release of Exim-4.94, transports refuse to use tainted data in
constructing a delivery location. If you use this in your transports,
your configuration will break, causing errors and possible downtime.
Particularly, the use of $local_part in any transport, should likely be
updated with $local_part_data. Check your local_delivery transport,
which historically used $local_part.
Unfortunately there is not much documentation on "tainted" data for
Exim, and to resolve this, non-official sources need to be used, such
as  and .