Problem of overload in large environment (2500 users)

Hello

We had upgrade our Zimbra from v6 to last v8.0.7, and make the installation of the last zextra suite with the chat module.

all was working well with few users, but when i had the 2500 users log on i had severals problems :

- we passed all our connexion thru a reverse proxy (httpd).
- i have a lot of "POST /service/soap/ZxChatRequest HTTP/1.1" 200 184 in the access log.
- in 5 minutes, i have a error that i reach the max client/process for httpd.

Is there's a way for the zimlet chat to be less conversative ? Or a advice when we passed thru a reverse proxy to access the zimbra server ?

Rgds,