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CloseDeveloper reply by Günter Gersdorf
Rated 4 out of 5 stars
This add-on seems to do exactly what I am searching for, but why does it require "full, unrestricted access to Thunderbird, and your computer"?
Deal-breaker for me, unless there is a pretty good reason.
Edit: thanks for your fast answer. I may reconsider.
Please read https://support.mozilla.org/en-US/kb/permission-request-messages-thunderbird-extensions#w_have-full-unrestricted-access-to-thunderbird-and-your-computer
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