This may be an FAQ but I looked at the Campaign Inspector and that wasn't particularly useful. Any insights on this would be appreciated.
The Marketing Calendar is a place to start but certainly won't track all emails sent in a day. Notable Trigger Based Emails would never be shown. Marketing Calendar - Marketo Docs - Product Docs
Yes, Chris' mention of the marketing calendar will work. I would create a new view of "Email scheduled" and you can bring in the filters for "Smart Campaign with email", "Email Program", and "Engagement Cast" and that will be a good place to start.