Unfortunately, they aren't even generating bounce messages, so we only realized this when several pieces of expected correspondence about the Future Fashion Folio never materialized.
It seems to be a very stealthy whitelisting requirement, and they don't make it easy for folks to put cc26.info on their whitelists.
Fortunately, we own cc26.org as well as cc26.info.
This means I'll probably be migrating the CC26 email system over to cc26.org in the course of the next several days. The cc26.info addresses will forward to the cc26.org addresses.
The website will stay at cc26.info for the moment, as I don't wish risk breaking the site.
A general announcement will go to registered members and be posted on the site when the change goes live.
You can repost or forward this information as appropriate.