Composed characters in email are not encoded

RT does not encode (RFC 1522) the composed characters in the header of
the email it sends:

Amavis complains (and rightly so):

X-Amavis-Alert: BAD HEADER Non-encoded 8-bit data (char C3 hex) in message header ‘Subject’
^

SpamAssassin thinks it’s probably spam:

X-Spam-Report:
* 2.4 TO_HAS_SPACES To: address contains spaces
* 2.7 SUBJ_ILLEGAL_CHARS Subject contains too many raw illegal characters

RT does not encode (RFC 1522) the composed characters in the header of
the email it sends:

Subject: [CODEV-NIC #80] Gestion des termes interdits et réservés

Amavis complains (and rightly so):

X-Amavis-Alert: BAD HEADER Non-encoded 8-bit data (char C3 hex) in message header 'Subject’
Subject: …] Gestion des termes interdits et r\303\251serv\303\251s \n
^

Hm. I thought there was code specifically to deal with that. A patch
would be appreciated.