Hey! Thanks for reporting this—a few folks have asked for DeepL specifically in the past. I agree it’s really much better than what we’re using now. Using it the way we’re supposed to (as an API customer) is one cent per 500 words, which could be too expensive for folks that have automatic translation enabled for most of their emails.
I’ll see if we can add this as an option of some sort though—we have enough of a system in place we could forward costs along if they became too high or degrade the translation quality after you hit 250,000 characters / mo ($5) or something like that.