Email Routing subdomain support, new APIs and security protocols

What this post added

This post introduces support for two new email security protocols: Authenticated Received Chain (ARC) and MTA Strict Transport Security (MTA-STS) for Cloudflare Email Routing. ARC preserves email authentication results (SPF, DKIM) through intermediate servers. MTA-STS enhances SMTP security by enforcing TLS connections. It also announces new Email Workers APIs that allow sending emails programmatically from Workers and further enhance incoming email processing capabilities.