Greetings,
Thank you for asking.
I am afraid it’s not possible.
Cloudflare doesn’t provide SSL certificate for e-mail traffic, nor proxies e-mail by default (except, we can use Cloudflare Spectrum product to protect some proxied ports even for e-mail but that requires setup and configuration on the client/server side).
E-mail Routing feature cannot help in your case.
If you want to have encrypted e-mail, that would have to be a valid SSL certificate being generated via Let’s Encrypt; ACME; Certbot, or purchased online.
Therefore, your MTA would have to be using this kind of type of encryption and be properly configured.
Cloudflare’s Universal SSL cannot help here, neither Cloudflare Origin CA Certificate which works only for Web traffic.
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