Hi Tina,
For our email campaigns, we add a step to check if contacts been sent at least 1 email during the last 3 days, if yes, they go into a wait step and the campaign will automatically keep checking every day until the contact is clear (have not receive at least one email in the last 3 days) then will send them the email.
The contact filter is just Sent Any Email and you can put in how many email within last x days.
This work really well for us.
Regards,
Angie