Cloudflare Spectrum Unlimited Email

I put together an email server on a Cloudflare Worker. It opens a TCP socket on 587, resolves the recipient's MX records and connects to their SMTP server.

In other words, you can send emails from Cloudflare's IP addresses. This would replace Outlook, Gmail, SES, MailChannels, etc. for sending emails, assuming it's reliable.

I'm really curious about IP reputation though, if it's Cloudflare's IPs, how often would emails go to spam?

I can't test the code without an Enterprise subscription, but I’m really curious to see what would happen.

As you mentioned, Ip reputation is the biggest concern. Cloudflare's IPs are primarily designed for web traffic, not email. Email providers heavily scrutinize IPs, and any unusual activity (like a sudden surge of emails from IPs typically used for websites) could trigger spam filters.

IP reputation is the least of your concerns.

Agreed that this would theoretically run on Cloudflare's Edge network.

The biggest would be this violating Cloudflare's acceptable use policy. Given that they explicitly prohibit connection to port 25 - https://developers.cloudflare.com/w...ockets/#connections-to-port-25-are-prohibited

Then you have the fact that Cloudflare's IPs are some of the most common IP used for web traffic.

Then you have the absolute lack of any PTR records. Further no DKIM, no DMARC, no SPF