Postfix not receiving mail from few domains

Hello, I really need your help here...

I've set up a postfix mail server for a single domain a couple months ago, and I'not able to receive mails from a few domains, always same ones.

After a tcpdump I found out that, when receiving mail, the mail server is not identifying itself when issuing the HELO command, instead of replaying:
"250-mail.mydomain.com says HELO to w.x.y.zort#"

it just replies:
"250-mail.mydomain.com"

Thanks in advance, Jose

 

Hello, which server you are using ?

Please try to telnet mail server & paste the output.

 

Hello, thanks for replying

I'm running Postfix 2.9.6 on Ubuntu 12.04.4 LTS

Here goes the output from a telnet session:
root@ns:~# telnet 1.2.3.4 25
Trying 1.2.3.4...
Connected to 1.2.3.4.
Escape character is '^]'.
220 mail.mydomain.com ESMTP Postfix
helo testfromdomain.com
250 mail.mydomain.com
mail from:[email protected]
250 2.1.0 Ok
rcpt to:[email protected]
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
To:[email protected]
From:[email protected]
Subject: Test by telnet
Msg Body

.
250 2.0.0 Ok: queued as 5F8DFEC0066
quit
221 2.0.0 Bye
Connection closed by foreign host.

 

Do you find any thing in mail.log?
Please paste your mail.log