How can I monitor response time to e mails from my team?

[Extra 300 Driver]

My team get about 1000 e mails a month and they are meant to reply to e mails with a set period of time. I want to monitor if they are responding to these withiut asking them to be 'honest'. I really want this to be automatic, or as fuss free as I can get it.

Can this be done through outlook or do I have to get a new application?

[Extra 300 Driver]

It is in house but we are contracting for a large company, so asking anything to be done to the server is out of the question

[Extra 300 Driver]

Thanks all, I'll take a closer look