emails sent to BCC list not received

I have a distribution list to which I periodically send messages using BCC. I usually send the messages from my iCloud.com email address using Apple Mail on my iMac. Starting about 2 weeks ago, every message I try sending to this group disappears into cyberspace. The message shows up in my sent mail, but none of the recipients receive the message. If I BCC myself, even I don't receive my own message. There are no bounce backs and no error messages. The email just goes away. My ISP is CenturyLink and they tell me that it's not a problem with their mail servers since I'm sending with an iCloud email address. Tonight, I tried sending to the same list from the same email address on my iPhone and the same thing happened. I even tried sending to the same list from the Mail app on iCloud.com and nobody received the message (including me). Any help would be appreciated.