I don't recall seeing this mentioned on the DL previously. Just FYI.
RFC 8255 supports multi-language content in email (see: https://tools.ietf.org/html/rfc8255). At IETF 101, Nik Tomkinson has organized a hackathon on Saturday and Sunday to test (and presumably improve) running code:
https://www.ietf.org/mail-archive/web/slim/current/msg01304.html
There is also a specification for language negotiation in SIP (https://tools.ietf.org/html/draft-ietf-slim-negotiating-human-language), but this will not be part of the hackathon.
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