Regarding issue #2:
If you look at the message source, all of those "wrong characters" are encoded as UTF-8 "EF BF BD". This is the 'REPLACEMENT CHARACTER' (U+FFFD) -- see
http://www.fileformat.info/info/unic...fffd/index.htm -- and indicates that the originating MUA can't represent the specified accented characters and is replacing them with U+FFFD.
Since this error is on the sender's end, there's nothing we can do to fix.