A delivery loop was detected which causes this email to be undeliverable

I have created a routing for one of the emails on my domains: [email protected] that was used before by Google Workspace.
I removed all the MX of Google, but when I am trying to send to this email I get this error message:

A delivery loop was detected which causes this email to be undeliverable.

I get it on the [email protected], not on the email address I actually sent to…

What can be the reason?