Emails being throttled and eventually time out. Why is this happening and how to fix?

Our church uses Outlook thru GoDaddy.  Each week we send out an email to our 135 members.  Frequently, but not always, the nineteen comcast.net emails are returned.  I submitted the IP Block form and am told our IP address is not being blocked.

Our DKIM, SPF, Mx, and DMARC records appear to be correct.

Reason: [{LED=451 4.2.0 Throttled - https://postmaster.comcast.net/smtp-error-codes.php#RL000010};{MSG=};{FQDN=96.102.18.147};{IP=96.102.18.147};{LRT=8/13/2026 2:13:03 PM}]. OutboundProxyTargetIP: 96.102.18.147.

Reason: [{LED=450 4.4.318 Connection was closed abruptly (SuspiciousRemoteServerError)};{MSG=};{FQDN=mx1.mxge.comcast.net};{IP=96.103.145.162};{LRT=8/13/2026 7:59:55 PM}]. OutboundProxyTargetIP: 96.103.145.162. OutboundProxyTargetHostName: mx1.mxge.comcast.net

I don't know why Comcast is blocking us, or throttling us, for nineteen emails.

Looking for help to resolve.

Thank you.