We track sales activities in general per SFDC user, in Salesforce. Whenever an email is sent to a prospect, an activity is logged, and the type of activity is logged as well. We use this for tracking response time of salespeople/SDRs.
As for deliverability, we haven't come across huge problems, because our sales people are sending out emails to individual prospects, not en-masse. We do train our salespeople on how to watch the marketing activity to make sure they're not overwhelming prospects with emails/communication. After the salespeople have gone through the training to make sure they're in line with marketing, it's their responsibility not to send the same email content if a prospect has already downloaded it.
If you're looking to track deliverability because your salespeople are going to be acting as marketers (i.e., sending out email blasts to lots of prospects), you might consider making actual Marketo programs that are available through SFDC. You could track deliverability that way, if that's the situation you're facing in your company!
Edward UnthankMarketing Operations Specialist
Yesler