I am keep getting below errors for few remote domain

Dec 18 11:42:36 mail2 postfix/smtp[3562]: 3926715F0011: to=<ld.singh@fluidyn.com>, relay=mx.mailbox.orange-business.com[194.2.0.80]:25, delay=61, delays=0.13/0.02/0.65/61, dsn=4.4.2, status=deferred (lost connection with mx.mailbox.orange-business.com[194.2.0.80] while sending end of data -- message may be sent more than once)

Requed several times but same.restarted zimbra service also. I am using Release 6.0.15_GA_2995.RHEL5_64_20111212142837 RHEL5_64 FOSS edition