Long Time Member getting message that he is blocked (black listed)

The member is Brian Woolf in Blue Moon Toastmasters. He's been a member for years but is now getting an error message saying he is "block (black listed)" from sending emails to member-585095@toastmastersclub.org. 

He is so frustrated that he says he will drop from the club unless this is resolved.
Please advise why this is happening and what I as site administrator can do to fix it.
Thank you,
Sharon Hill

The correct web address is: 585095.toastmastersclubs.org
Pls use that.

Also use members - 585995@toastmastersclubs.org to transmit to all members

Correction members-585095@toastmastersclubs.org

Hello, Les. Thank you for your quick response.
But I don't understand. Brian is the only member getting this black list error.
Is there something specific that Brian should do?

Sharon

Black listIf you are getting unwanted emails from just a few places or people, you can put the names in this list.They can be specific email addresses, or whole domains. Entering a whole domain in a blacklist will stop email from anyone whose email address ends with that domain. For example, it will block  This email address is being protected from spambots. You need JavaScript enabled to view it. ,  This email address is being protected from spambots. You need JavaScript enabled to view it.  and everyone else from bannedaddress.com That applies even if one of those addresses is in the white list.Enter each name or domain, separated by commas, and save.