Confusion about allowing missing MAIL FROM

Hello list,

I saw something in my qpsmtpd.log this evening which struck me as
unusual.  In one particular incoming message, the MAIL FROM was not
there.  A quick telnet session reproducing it follows, followed by the
list of active plugins.

I'm not aware of there being a good reason for allowing this behavior,
but I'd be happy to be told otherwise.

Also, for what it's worth, I've tried this with and without
'dont_require_anglebrackets' enabled, both resulting in the same
behavior.  Ultimately, I'm curious if this is expected, or if I've found
a bug.

Best regards, and thank you for the great program.

-- log output --
220 myhostname ESMTP qpsmtpd 0.84 ready; send us your mail, but not your
spam.
helo myhostname
250 myhostname Hi myotherhostname [myip]; I am so happy to meet you.
mail from:
250 <>, sender OK - how exciting to get mail from you!
rcpt to:me@myhostname
250 <me@myhostname>, recipient ok
data
354 go ahead
quit
221 myhostname closing connection. Have a wonderful day.
-- end log output --

-- plugins --
hosts_allow
dont_require_anglebrackets
check_earlytalker
count_unrecognized_commands 4
check_relay
require_resolvable_fromhost
rhsbl
dnsbl
check_badmailfrom
check_badrcptto
check_spamhelo
check_validrcptto_cdb cdb_file validrcptto.cdb qmail_ext -
spamassassin reject_threshold 7.5 leave_old_headers keep
rcpt_ok
queue/qmail-queue /var/qmail/bin/qmail-queue
-- end plugins --

-- 
Glen Barber