This is exactly what the Exchange Round-Trip Email monitor is for. This monitor performs the entire sequence of sending an email and retrieving it using the same subsystems users would. Anything that prevents ipMonitor from doing the full transaction indicates a failure.
My advice is to add and configure the Exchange Round-Trip Email monitor, and create a report just for this monitor.
Not looking specifically for exchange, but rather other services (ie. NTP, SMTP, Internet Access) such that I can monitor 6 external websites for connectivity, however if one of these monitors goes down for whatever reason (maintenance, etc) my overall uptime of my GROUP is not affected unless they are ALL down, in which case I have a serious outage.
Another example - we have two DNS servers, if I drop one, I still have DNS services running, so I would like to report 100% for service uptime, however if I drop both servers (services) my report should show downtime. Kind of reverse dependencies...!