I just did a quick test with the Email Routing Beta and this is what I noticed:
It appears to be something more like a networking proxy, which is different than what I’m used to for this type of mail service.
The service isn’t dealing well with greylisting because it took up to 2 additional attempts to pass the greylisting test due to different IP addresses being seen by the receiving server. It would be better to remember which IP address made the first attempt, and, if possible, remember for 35 days since the last attempt.
If the service is intending to hide the receiving mail server, then some things probably need to be made clear to users:
FCrDNS, DMARC, SPF, and DKIM tests all make DNS lookups that are trivial to configure for revealing the IP address of the mail server.
However, if the primary purpose of the tool is make it easy to have email forwarding to compete with other registrars and save me the hassle of configuring mail records on domains that just need to receive occasional confirmations, or something, it’s fine.