I google and found my answer from ZCS support page:
Bug 11299 – Allow user to set multiple forwarding addresses, need admin defined limit

> > Currently, we allow
an admin to set multiple forwarding addresses
> > for an account by setting zimbraMailForwardingAddress, but the end
> > user doesn't have access to this. The end user settable one
> > (zimbra*Pref*MailForwardingAddress) is single valued in the LDAP
> > schema. Making it multi-value also requires making sure there is an
> > admin set limit on how many you are allowed. Let me know if you
> > want us to add an enhancement request for this.

Yes, that would be nice. We have multiple (>60) users using this feature.
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I have 50 members need to receive my automatic forwarding email in daily basis.
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Question: Is ZCS Open Source Edition able for multiple addresses forwarding?