ArgumentError: invalid byte sequence in UTF-8 when sending ISO 8859-X encoded Mails about helpy_imap HOT 2 CLOSED

As this issue was preventing us from using helpy_imap effectively, I implemented a workaround for this problem which leaves room for improvement I guess.
Most emails we get are already encoded in UTF-8, but there are some that are in ISO 8859-1 which is in line with the numbers here: https://w3techs.com/technologies/history_overview/character_encoding. (92% UTF-8, 3,9% ISO 8859-1, for websites). Based on that I assume that there won't be a significant loss by misrepresented characters when we first convert ASCII-8BIT messages to ISO-8859-1 which is an extension for US ASCII. The downside might be that is not the most performant thing to do and therefore I would appreciate if someone has a smarter idea :)

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After some more testing I figured out that I made a mistake and that the proposed fix did not have the desired effect.
As I couldn't figure out why the "real" encoding of the @email variable does not represent the encoding of the raw email I came up with a different approach.
I added two checks if entity.force_encoding returns a String with valid encoding to distinguish UTF-8 and ISO-8859-X Strings, even if entity.encoding.name is just ASCII-8BIT which solved the problem for me.

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