Everything right up to the email render is correct - the Web page us using UTF-8 and returning the ™ symbol as three bytes (Unicode character inspector: ™) E2 84 A2
In your final email you can see these three bytes as â ¢ - This is Those same three bytes being rendered using either ISO 8859-1 or ISO 8859-15 the single byte representation of non ASCII characters we used before Unicode was a common thing. E2 is â and A2 is ¢ - 84 is not defined in there. (ISO/IEC 8859-15 - Wikipedia)
The issue is that the Email is not correctly defining its contents as utf8 and so the rendered is falling back tio 8 bitl. At least that’s how it looks - if you look at the source of the email (a) is it really these three bytes or has it done some off translation to three unicode characters and (b) what charset is actually defined in the raw email content.