Thank you for reaching out to the Community! I can understand how important it is for your emails to deliver to your contacts. I have taken a look at your most recent campaign. The email addresses with these domains do appear to have all bounced as either other or blocked. Do you know if these domains have made any recent updates to their security settings? Blocked bounces generally happen when the ISP has decided not to deliver an email campaign. While on the other hand, the other bounce is when the ISP bounces with an unreadable or non-standard error coding. Are these contacts continuing to bounce after whitelisting Constant Contact? We also have this article in our Help Center that goes over the different types of bounces and how they can be managed.
Constant Constant customer support did not do much to help us with this problem. We analyzed our bounces and determined that centurytel, centurylink, and embarq were the only ISPs bouncing our emails. We further discovered that links within the emails were causing the bounces, but this had not been a problem in the past and we still have not determined how to deal successfully with the problem ISPs. We were disappointed that customer support offered only generic solutions to our problem instead of looking more deeply into the cause, as we have tried to do ourselves.