[exim] Non-us-ascii character in sender address

Debian Buster, exim4 4.92-8+deb10u1

In sender address a unicode (U+FEFF) character (Zero Width No-Break Space (BOM, ZWNBSP))

2019-07-23 18:17:07 1hpxTO-0005QR-9B <= Kevin<feff>Smith@??? H=(losaass.it) [193.106.43.215]
I=[193.197.165.21]:25
2019-07-23 18:17:07 1hpxTO-0005QR-9B => xxx <xxx@???>
2019-07-23 18:17:07 1hpxTO-0005QR-9B ** xxx@??? R=sophos T=remote_smtp H=10.157.x.x
I=[193.197.165.21] X=TLS1.2:RSA_AES_256_GCM_SHA384:256 CV=no: SMTP error from remote mail server
after pipelined MAIL FROM:<Kevin\357\273\277Smith@???> SIZE=10231: 500 non-US-ASCII
characters are not allowed in SMTP commands

Next Hop, a Sophos UTM, rejects sender, Exim does not?