The default value of the max number of recipients is set to 100.
Originally Posted by ben1967
To change this value you have to modify the 'smtpd_recipient_limit' attribute:
postconf -e 'smtpd_recipient_limit = valore'
Maybe you can look at the PolicyD integrated with zimbra 7.
also other configurable things like max emails a user can send a day , and the time between subsequent emails
With the quota module enabled, you can activate a message counter based on sender; for more info:
Quotas | Policyd
[HowTo] Enabling CBPolicyD in Zimbra 7.1.1