Unable to send big (4Mb) attachment without webmail

[sadiq007]

Hi,
From Webmail i am able to send attachment up to 15 Mb, but from Outlook i can send attachment only up to 3Mb, if i send attachment more then 4Mb size? then i am getting error
"451 4.7.1 Service Unavailable - try again later Server Error:451"

while looking zimbra.log
Jun 21 17:35:45 mail postfix/cleanup[17046]: 6B9007DC01CC: milter-reject: END-OF-MESSAGE from unknown[210.211.2.1]: 4.7.1 Service unavailable - try again later; from=<user1@mydomain.com> to=<someone@gmail.com> proto=ESMTP helo=<administrator>

(i am having zimbra 7.1.0 64 bit)
what to give at Milter Server Bind Address: Under Server settings-MTA-Milter Server ??

[manolopm]

Hi:

Seems to be a timeout between the milter server and postfix. When the cleanup server pass throught the conections it cuts off them.

We solved it adding:

milter_default_action=accept

into main.cf

Let us know if this solve it for you