Thank you for reaching out to the Constant Contact Community!
I have taken a look at the engagement for a number of those addresses that you mention and I am not seeing a single successful delivery. I am wondering if these are actually valid addresses as I see they are bouncing as “Undeliverable”. In most cases this means that the address does not actually exist. I don’t think they are blocking Constant Contact emails otherwise the bounce reason would be “Blocked”.
Click Here for more information on our bounce categories. Please let us know if you have additional questions.
Thank you for using Constant Contact, have a great day!
Customer Engagement Specialist
If you find my post helpful, and it answers your question, please mark it as an "Accepted Solution"
by clicking the Accept as Solution button in the bottom right hand corner of this post. Increase your profitability by integrating your email marketing and social media. Download this guide and learn how you can achieve great results with email marketing and social media combined!