Eduardo - I had a second so I did a quick check. Looks like you need to convert to Base64 when submitting to the api... so there's probably some testing and research you'll need to do.
I haven't dealt with this myself - but this is where I'd start....
What I found -
https://developers.google.com/gmail/api/guides/sending - Mail API
RFC 2822 (https://datatracker.ietf.org/doc/html/rfc2822)
Found this conversion for js - https://github.com/googleapis/google-api-nodejs-client/pull/1088
const utf8Subject = `=?utf-8?B?${Buffer.from(subject).toString('base64')}?=`;
doing something similar with jinja/formula field might be possible? dunno.
aged stackoverflow suggestion - https://stackoverflow.com/questions/61905243/does-gmail-restful-api-support-sending-of-non-ascii-emails-addresses#:~:text=At%20the%20moment%20of%20this,able%20to%20send%20the%20emails.
------------------------------
joe vandervest
------------------------------