Hello @LeeP248. Constant Contact sends from many different IP addresses, which are different from the ones that you send from using your Outlook email client. An email address goes into a suspended status after our system tries to send a few times to the address and it bounces. While an address is in suspend, we do not send any campaigns to them during that time. Sending to bounced addresses can have a negative impact on your deliverability rate so this is why the suspended status exists.
If you have further questions about these suspended email addresses, you can reach out to our Deliverability team at 866-433-8499. They are available Monday through Thursday from 7am-11pm ET and Friday from 7am-9pm ET.