[Exim] Syntactically correct?

Hello all,

My question is why does Exim accept a simple <> in the 'From' part of the
SMTP conversation?

It goes like this:

220 myserver.com ESMTP Exim 3.16 #1 Sat, 30 Dec 2000 17:48:53 +0100
HELO myclient.com
250 myserver.com Hello myclient.com [1.2.3.4]
MAIL FROM: <>
250 <> is syntactically correct        

Is this the desired behavior?

When receiving such mail, the From line appears as "Remote Mail Delivery
System <>"

How can I reject messages with <> in MAIL FROM part?

Thanx:
          Pocok