Error 503 after configuring Exim to use Mailscanner on Debian Sid

[Tóth Attila]

I'm using Debian Sid with the latest Mailscanner package and all other
related packages:
Exim-tls: 3.35-3
Spamassassin: 2.31-2
Mailscanner: 3.14.1-2

After setting it up according to the instructions I've found in the
package and also on the web page, the MTA stopped delivering mails.
I tried to have a closer look on the problem, so I tried to send a mail
using telnet from another host.

I got the following results:
(I substituted realworld names an IPs)

user at tryhost:~/$ telnet myhost.hu 25
Trying 193.225.82.157...
Connected to myhost.hu.
Escape character is '^]'.
220 dc.sote.hu ESMTP Exim 3.35 #1 Sun, 30 Jun 2002 01:07:34 +0200
helo tryhost.hu
250 myhost.hu Hello tryhost.hu [correct IP address]
mail from:user at tryhost.hu
250 <user at tryhost.hu> is syntactically correct
rcpt to:user at myhost.hu
451 <user at myhost.hu> All deliveries are deferred
data
503 Valid RCPT TO <recipient> must precede DATA
quit
221 myhost.hu closing connection
Connection closed by foreign host.

So it seems to me, that the MTA couldn't interpret the RCPT command
properly. I'm not suprised, that no mails were delivered.

Could it be the problem that I use sender and receiver verification?

Question: what did I do wrong?

Tóth Attila, Semmelweis Egyetem ÁOK VI.
1031, Bp. Rozália u. 37., 242-6765