Comment by lproven

I've been on email since 1985 and had the same personal address since 1991. I've used about 20 or 25 email clients across a dozen OSes (counting all Linux distros as one).

Gmail has the best search of any email system I've found.

I think your problems are nothing to do with Gmail or its search, but are to do with things like Unicode character encoding, character sets and codepoint matching.