[exim-dev] Exim trying "DATA" with no valid "RCPT"

I ran a test a moment ago and got this result:

Connecting to foxtrot.kis.keele.ac.uk [160.5.46.69]:25 ... connected
SMTP<< 220 foxtrot.kis.keele.ac.uk Keele University Electronic Mail Service
SMTP>> EHLO pc67.isc.keele.ac.uk

  SMTP<< 250-foxtrot.kis.keele.ac.uk Hello pc67.isc.keele.ac.uk [160.5.50.10]
         250-SIZE 8388608
         250-PIPELINING
         250 HELP

SMTP>> MAIL FROM:<csa01@???> SIZE=1459
SMTP>> RCPT TO:<doesnotexist@???>
SMTP>> DATA
SMTP<< 250 OK
SMTP<< 550 Unknown user
SMTP<< 503 valid RCPT command must precede DATA
SMTP>> QUIT

This is EXIM 4.43 with the exiscan patch. The order of the lines implies
that Exim sends a "DATA" command before it sees the response from the RCPT
command. Surely Exim shouldn't be trying to send the message unless at
least one RCPT command succeeded?

-- 
  ______    jonathan@???    Jonathan Knight,
    /                                  Department of Computer Science
   / _   __ Telephone: +44 1782 583437 University of Keele, Keele,
(_/ (_) / / Fax      : +44 1782 713082 Staffordshire.  ST5 5BG.  U.K.