Weird things in the mail queue

[Lionel Elie Mamane via dovecot]

I noticed a mail stuck in my mail queue. dovecot-lda was returning
error 64 Invalid parameter given. (EX_USAGE).

Weird, weird, weird. After some sleuthing, I found the sender address
was firstl...@domain.tld, with a UTF8-encoded Unicode U+FEFF ZERO
WIDTH NO-BREAK SPACE character (AKA byte order mark) between "First"
and "Last" :)

Since that is passed as the -f parameter to dovecot-lda, it was giving
the 64 error.