mail recieve rejected

[miza]

Hi, i have problem to recieve mails from specific provider, and the failure message is this:

Code:

Nov 3 18:33:36 sphinx postfix/smtp [19196 2.6] DAB5D1E40665: to=<kontra@eksegersi.gr>, relay=mail.eksegersi.gr[78.47.186.84]:25, delay=3.1, delays=0.01/0.02/0.21/2.9, dsn=5.7.1, status=bounced (host mail.eksegersi.gr[78.47.186.84] said: 550 5.7.1 <kontra@eksegersi.gr>: Recipient address rejected: Mail appeared to be SPAM or forged. Ask your Mail/DNS-Administrator to correct HELO and DNS MX settings or to get removed from DNSBLs; please relay via your ISP (eklogika.gr) (in reply to RCPT TO command))

DAB5D1E40665: to=<kontra@eksegersi.gr>, relay=mail.eksegersi.gr[78.47.186.84]:25, delay=3.1, delays=0.01/0.02/0.21/2.9, dsn=5.7.1, status=bounced (host mail.eksegersi.gr[78.47.186.84] said: 550 5.7.1 <kontra@eksegersi.gr>: Recipient address rejected: Mail appeared to be SPAM or forged. Ask your Mail/DNS-Administrator to correct HELO and DNS MX settings or to get removed from DNSBLs; please relay via your ISP (eklogika.gr) (in reply to RCPT TO command))

How can i fix this problem?