FTH3 blocking emails to members

What additional information can you provide to help me correct this error? Thnx.

From: FreeToastHost Server <server@toastmastersclubs.org>
Date: August 19, 2021 at 4:33:18 AM MDT
To: '2977 club coordinator'
Subject: [FreeToastHost] Message Not Delivered: Cherry Creek Toastmasters' Weekly Meeting Information
loganmacmillan@centurylink.net was skipped because it has previously bounced too many times. Please visit support.toastmastersclubs.org and post a support request message for more information.

Their email is flagging email from FTH as spam. They need to whitelist
server@toastmastersclubs.org and agenda@toastmastersclubs.org

Your email message to loganmacmillan@centurylink.net could not be delivered
and was returned to the FreeToastHost server. Details are as follows:

Recipient Email Address: loganmacmillan@centurylink.net
Email Subject: Cherry Creek Toastmasters' Weekly Meeting Information
Date Sent: Thu, 12 Aug 2021 03:39:59 -0700

Diagnostic Code: 554 5.7.1 [VI-101] Message blocked due to spam content in the message.
Delivery Status: 5.7.1 securityerror
Date Last Attempted: Thu, 12 Aug 2021 10:40:14 GMT

The Bounce Count for Email Address [loganmacmillan@centurylink.net] has been reset to zero.