On my team, Differential revisions often have specific reviewers as well as project reviewers. My project tends to get a lot of review requests, so I'd really like to apply a server-side mail filter that only matches messages about revisions where I am specifically listed as a reviewer. For example, I might choose to keep emails about reviews for me in my inbox and move the rest to a "Reviews" folder.
It looks like Phabricator has great support for this via the X-Phabricator-To header. Unfortunately, my server-side mail rule infrastructure doesn't allow matching on custom headers, so I'm not able to use it to set up this kind of filter.
My team's current code review system is configured to send email with the explicitly-specified users in the "To" field and the review project users in the "Cc" field. Because the server-side rules do allow matching on these headers, this allows me to set up a rule that does what I want.
It would be super helpful if Phabricator offered a way to do something similar, either by Cc'ing project reviewers or, alternatively, by providing an option to send email to a mailing list address associated with a project instead of addressing each individual member of the project.