Iam using zimbra 6.0.1 opensource version.
Iam getting the following error in zimbra log

Dec 22 19:50:58 pop postfix/smtp[32526]: 7FBB84A1916: host gmail-smtp-in.l.google.com[209.85.222.27] said: 451 Local Error (in reply to end of DATA command)
Dec 22 19:51:02 pop postfix/smtp[32591]: 330F04A17AA: host gmail-smtp-in.l.google.com[209.85.222.27] said: 451 Local Error (in reply to end of DATA command)

Thanks in advance for solving this error.