Hello there @ChefV5 !
Thank you for coming to the community to ask this great question.
Suspended emails can definitely sound tricky to manage but I promise it is simple! Let me explain. How we flag emails as suspended is basically once an an email address bounces for the first time as non-existent, Constant Contact puts a temporary 15-day hold on the email address. During this time, our system won't let anyone send emails to it. Any attempts to send to it by any customer results in a "Suspended" bounce. So, even if you haven't sent to an address before or if you've sent successfully to an address in the past, if the contact becomes suspended in any Constant Contact account, it bounces as "Suspended" in your account too.
After the temporary suspension is lifted, we allow email to be sent to the email address again. Only new emails scheduled to send after the hold is lifted are sent to the email address; we don't retroactively send emails that were scheduled while the email address was marked as "suspended".
If the email address bounces as "non-existent" again, the email address is then placed on indefinite hold and will again appear in your Suspended report if you attempt to send to it.
Because of this, we recommend that they are removed from the account as it's unlikely for those emails to ever be active again. You can find out how to remove these suspended email addresses from your account here