Restrcting Zimbra Server

[abhiz]

When I try to send out email to yahoo.com or any other public domain I get the below message and my emails get deferred temporarily

http://help.yahoo.com/help/us/mail/defer/defer-06.html

is there any way so that I can restrict my mail server like

1. Send only 60 emails per domain in 10 minutes (just example)

2. open only 3 SMTP connection with any public domain SMTP.

[uxbod]

Have you asked them why they are deferring your email ? are you users spamming Yahoo ?