How to revert forwarded club position e-mail addresses to @toastmastersclubs.org

All of our club position email addresses are currently listed with an "@ customdomainname.com " (within the "Email and Contact Forms" module, on the "Club Email Addresses" tab). How can I revert these custom domain email addresses to the original "position-####@toastmastersclubs.org email addresses?  There is no option to edit those addresses. Thank you in advance. Club #6294  FYI- the current emails do not forward. 
 

To fix the forwarding issue with the custom domain addresses; in your domain account check your DNS A and MX records against the settings instructions in this document;

support.toastmastersclubs.org/doc/item/dns-settings-overview

The default email aliases (@toastmastersclubs.org) are always active if you chose to use them.

Remove the custom domain from the admin panel and all will revert to the *-nnnnn@toastmastersclubs.org