I just did an upgrade as well, and my settings seem OK. I don't think there's anything within the zimbra domain for this, but for the proxy & mailbox:
Here's what I have (allows 80 & 443) --- not sure these are the best settings!!
[zimbra@zproxy ~]$ zmprov -l gs zproxy.example.org | grep -i http
zimbraHttpNumThreads: 250
zimbraHttpSSLNumThreads: 50
zimbraMailMode: http
zimbraReverseProxyHttpEnabled: TRUE
zimbraReverseProxyMailMode: http
[zimbra@zproxy ~]$
[zimbra@zproxy ~]$ zmprov -l gs zproxy.example.org zimbraReverseProxyMailEnabled
# name zproxy.example.org
zimbraReverseProxyMailEnabled: TRUE
[zimbra@zproxy ~]$
#Mailbox server
[zimbra@zproxy ~]$ zmprov -l gs mbx1.example.org zimbraReverseProxyLookupTarget zimbraReverseProxyMailEnabled zimbraMailMode
# name mbx1.example.org
zimbraMailMode: http
zimbraReverseProxyLookupTarget: TRUE
zimbraReverseProxyMailEnabled: FALSE
[zimbra@zproxy ~]$
Additional Information:
Working with Zimbra Proxy