[Exim] Why not pernitted to send mail ?

A remote mail server do not want to accept mail from our server.
Could you please give me hint what can be a problem ?
I tried exim -v -bt and I think it looks O.K.

exim -v -bt ondrej.skvarek@???
ondrej.skvarek@???
deliver to ondrej@???
router = lookuphost, transport = remote_smtp
host alpha.fri.utc.sk [158.193.138.1] MX=0

Here are the logs of SMTP mail echo tests
for the same server and for two other servers executed from
my client PC. The responses from them are different. Could you
please explain what does it mean "may be forged" in the second
test log.

SMTP Mail Echo Test
Server Name: 158.193.138.1
Oct 05 08:37:56 connect: IP address:158.193.138.1 Port:25
Oct 05 08:37:56 recv: 220-alpha.fri.utc.sk Smail-3.2.0.102 (#2 1998-
Oct-13) ready at Thu, 5 Oct 2000 08:33:50 +0200 (CEST)
Oct 05 08:37:56 send: HELO isnopko.novitech-za.sk
Oct 05 08:37:56 recv: 220 ESMTP supported
Oct 05 08:37:56 send: QUIT
Oct 05 08:37:56 recv: 550 You are not permitted to send mail
SMTP Mail Echo Test: failed


SMTP Mail Echo Test
Server Name: 194.152.146.76
Oct 05 08:35:52 connect: IP address:194.152.146.76 Port:25
Oct 05 08:35:53 recv: 220 rsmail.novitech.sk ESMTP Sendmail
AIX4.3/8.9.3/8.9.3; Thu, 5 Oct 2000 08:31:04 +0200
Oct 05 08:35:53 send: HELO isnopko.novitech-za.sk
Oct 05 08:35:56 recv: 250 rsmail.novitech.sk Hello
novitech.za.nextra.sk [195.168.68.12] (may be forged), pleased to
meet you
Oct 05 08:35:56 send: QUIT
Oct 05 08:35:56 recv: 221 rsmail.novitech.sk closing connection
SMTP Mail Echo Test: successful


SMTP Mail Echo Test
Server Name: 194.212.171.130
Oct 05 12:20:57 connect: IP address:194.212.171.130 Port:25
Oct 05 12:21:01 recv: 220 email.cz ATCO SMTP server v.3,
welcome!
Oct 05 12:21:01 send: HELO isnopko.novitech-za.sk
Oct 05 12:21:01 recv: 250 email.cz Hello 195.168.68.12, I'm ready.
Oct 05 12:21:01 send: QUIT
Oct 05 12:21:02 recv: 221 email.cz Closing connection, bye.
SMTP Mail Echo Test: successful