Good evening Avery,
The error "connection refused" indicates that the sending IP address is on our perimeter block. To determine why the IP is being blocked, and request removal of the block, please submit an IP research request to SaaS_falsepositives@mcafeesubmissions.com
Please be sure to include the affected IP address (or range) in your email.
I hope this helps!
System Support Specialist
SaaS Email and Web Security
McAfee. Part of Intel Security.