That error is not relevant to you issue and is common on Plesk based VPS systems (or shared hosting). If a big provider drops your connection it will usually be for one of these reasons:
*. Connecting IP is blacklisted {common with cheap hosting accounts on shared servers that spammers use}
*. Missing, bad or plain broken DNS records (PTR, mx, spf)
*. Bad server conf (Qmail sends the HELO/EHLO with a name like 'localhost' or some other bad hostname)

There are others, but the majority of 'I can't send email to some providers' will usually fall into one of these areas if the network is all good - which we've established it is.

Without the raw logs to work with it's impossible to see the reason for the error and the best I can offer is to ask you to send me an email from that server and I'll see if the IP / transaction has any errors on the receiving end. I'll PM you and address to use.

here's some new info:

I got that From: MAILER-DAEMON@XXX-XX-XXX-XX.local
this mail is the one i receive from all the failure notice that my e-mails were not being delivered.

I've left you a Private Message with an email address. Send one to me there and I'll look in my logs and see why you are being rejected.

WARNING! Do not try the TELNET example given to gmail! GMAIL provide a feed to the CBL and any spoofing of this nature will get the IP you run it from listed with the CBL (and subsequently Spamhaus). So don't try it at home (or at work for that matter).....