domain blocked?

Hi T.RonD ,

Here's information on blocked bounce types, from our article on managing and preventing bounces:

When an email address bounces as blocked, the ISP has decided not to deliver to it. This is usually due to reputation, content (images, links, text strings, etc.), or a policy/filter on the recipient’s end.

The Causes:

• If you’re sending from a “free” email account as your From Address, some domains may reject your email. This could be corrected by using your own domain. (not applicable in your situation)

• If you’re seeing blocked bounces from small, private domains (such as a business or organization) we’ve found that hearing from their own users who want to receive our email often yields the fastest results, so we’ve created some form letters to help you communicate with the ISP directly.

• If neither of these are applicable, or if you're getting blocked bounces from a larger domain (Yahoo, Gmail, etc.) contact our Support Team to get it resolved.

In your situation, since it's a large group of contacts under a specific domain blocking your emails, it means that either the domain has blocked you or has blocked us. It could also potentially be an issue of rate limiting, similar to what Yahoo-managed domains like SBCGlobal and AT&T do in the US. In either case, I'd recommend speaking with our Delivery team directly, to get some more specific insight on your particular situation, and then consider looking into the second point (having those contacts reach out to their ISP / network IT).