It would be very nice for Mail Redirect to have redirect as an action in the filters. I tried Mail Redirect and it works great from the menu, but I have no need for a manual redirect function.

I have been using Redirectfilter for this, but it appears to be unsupported and and broke sometime around November. I did manage to load it by setting "extensions.strictCompatibility" to false in Thunderbird, but it has a lot of issues. Running Redirectfilter config locks up Thunderbird. I did manage to get it to work again with its default config by deleting some lines in Redirectfilter.js.