Greetings - We have delivered a backend service package to production which includes: 

• Combined and modified queries within the import checkout process to improve performance, reduce database load and reduce the amount of multi-processed imports.
• Added a system check at the time of sending an email batch that will reject the transactions if  the the email address is:  1) Unsubscribed or 2) already on the Bounced list. The functionality for sending emails has not changed. This check was added to reduce the number of transactions we pass forward to the transactional send API. 

If you have any questions or concerns, please reach out to our team at [email protected].