iRule to disable APM not working as expected

If your request has any of the apm cookies, you may need to remove them from that request. I've had weird issues like that.

so, perhaps your iRule could do something like this:

when HTTP_REQUEST {    
    if {[string tolower [HTTP::header "User-Agent"]] contains "mac os x"  && [string tolower [HTTP::uri]] equals "/ews/exchange.asmx"} {
        log local0. "  Disable access for [HTTP::uri]"
        ACCESS::disable 
        HTTP::cookie remove "MRHSession"
        HTTP::cookie remove "LastMRH_Session"
    } else {
        log local0. "  [HTTP::uri]"
    }
}