Exchange server smtp error 500 5.3.3 Unrecognized command

Hi,

I have a problem with commonication between two Exchange servers 2003.

exAsrv-FWsiteA----VPN------FWsiteB----exBsrv

Where:
exAsrv - Exchange 2003
exBsrv - Exchange 2003
FWsiteA - Cisco ASA5505 ver 7.2(2)
FWsiteB - Cisco ASA5505 ver 7.2(2)

Problem is when I try to comunicate with both servers on port 25.

1.
a)From exAsrv.mydomain.local I can telnet to port 25 to exBsrv.mydomain.local, but I see:
220 ****************************************************************************
*****************************************
helo
500 5.3.3 Unrecognized command

b)From exBsrv.mydomain.local I can telnet to port 25 to exAsrv.mydomain.local, but I see:
220 ****************************************************************************
*****************************************
helo
500 5.3.3 Unrecognized command

From RFC I have only information which I don't understand, why command line to long???
      4.2.1.  REPLY CODES BY FUNCTION GROUPS

         500 Syntax error, command unrecognized
            [This may include errors such as command line too long]

2. Another test. I enabled possibilyty on both exchange servers to comunicate on port 252:
a) From exAsrv I can telnet to port 252 to exBsrv, but I see:
220 exBsrv.mydomain.local Microsoft ESMTP MAIL Service, Version: 6.0.3790.3959
ready at  Fri, 8 Feb 2008 14:43:58 +0100
helo
250 exBsrv.mydomain.local Hello [192.168.1.200]

b)From exBsrv I can telnet to port 252 to exAsrv, but I see:
220 exAsrv.mydomain.local Microsoft ESMTP MAIL Service, Version: 6.0.3790.1830
ready at  Fri, 8 Feb 2008 14:45:07 +0100
helo
250 exAsrv.mydomain.local Hello [192.168.0.17]

On the site B exchange server is available from outside as a main server, however I want to
set up replication of both server. But now it is not a problem.

I checked configuration on both cisco routers:
1. NAT rules are setup correctly.
2. I disabled ESMTP inspecion on both sides.

Trraffic seems like is going correctly.

3.
a) Test telnet from host1B.mydomain.local(winXP) to exAsrv.mydomain.local to port 25.
220 ****************************************************************************
*****************************************
helo
250 exAsrv.mydomain.local Hello [192.168.0.23]

b) Test telnet from host2B.mydomain.local(GNU/Linux) to exAsrv.mydomain.local to port 25.

Connected to 192.168.1.200 (192.168.1.200).
Escape character is '^]'.
220 *********************************************************************************************************************
helo
250 exAsrv.mydomain.local Hello [192.168.0.5]

c) Test telnet from host2B.mydomain.local(GNU/Linux) to exAsrv.mydomain.local to port 252

Connected to 192.168.1.200 (192.168.1.200).
Escape character is '^]'.
220 exAsrv.mydomain.local Microsoft ESMTP MAIL Service, Version: 6.0.3790.1830 ready at  Fri, 8 Feb 2008 15:17:04 +0100
helo
250 exAsrv.mydomain.local Hello [192.168.0.5]

d) Test telnet from host3B.mydomain.local(WinXP x64) to exAsrv.mydomain.local to port 25.
220 ****************************************************************************
*****************************************
helo
500 5.3.3 Unrecognized command
e) Test telnet from host3B.mydomain.local(WinXP x64) to exAsrv.mydomain.local to port 252.
220 exAsrv.mydomain.local Microsoft ESMTP MAIL Service, Version: 6.0.3790.1830
ready at  Fri, 8 Feb 2008 14:45:07 +0100
helo
250 exAsrv.mydomain.local Hello [192.168.0.32]


Does one of you see any regularity as I don't.

Where can be a problem?

I think that somwhere in Windows, but don't see any regularity.
Please note I tested it when software FW are disabled on both sites.

Thank's for any suggestion.