Is there a specific set of tags in the headers of a SOAP request to the user service that will force the response to contain the refresh/notify elements?

We use the SOAP API to integrate one of our sites with Zimbra. One integration is to show users the number of unread e-mails in their INBOX on our site. We had been sending a NoOpRequest, without any special header content, to try to get the refresh/notify content and that appeared to be working fairly well until recently. We installed Zimbra Proxy and now we don't appear to be getting back the refresh/notify a lot of the time anymore.