Email failover issue

We have 2 MX records configured for our email. We have a firewall that is handling 2 ISP sources, Comcast and ATT. We are trying to setup that if Comcast goes down any emails sent are received via the ATT IP. We have confirmed that the server is reachable via both public IPs via telnet and an SMTP test, however when we block port 25 to simulate Comcast going offline emails are not received and the sender gets a permanent error message. Comcast is set for priority 10 and ATT is set for 11. We can’t figure out why it’s not working. Since the email server never receives the email if Comcast is down it seems like something outside of our network/firewall, like a setting on Cloudflare we need to change?

Cloudflare has absolutely nothing to do with email connections, other than providing plain DNS records that point to your servers. I say “plain” because all email-related DNS entries should be :grey: DNS-Only (not proxied our routed through Cloudflare in any way).

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The entries are set to DNS-Only. I’m not sure why it’s not working. If I block port 25 in my firewall from the Comcast IP I never get any emails, but if I specifically use the ATT IP address and an email test I get the email. It “seems” like the 2nd MX record is being ignored. I can also telnet and get an answer if I test via IP, so I know the ports are set properly.

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