Using the Email Rounting Beta parallel to an external mail service

I am about to start using a mail provider that restrict the number of incoming and outgoing email that can be sent daily (migadu).

I would like to use Cloudflare Email Routing Beta to receive email (forwarded to a gmail account) and this other external email provider to send email.

Is this technically possible? My understanding is that this is not possible with the “send as” feature of gmail, but is it possible some other way?