Slightly tangential, but is there something for RSpamd, where it can be run as just a blind mail relay?

I.E. like this:

  Internet Email (SMTP) -> [MTA + Rspamd] -> [Real MTA + Inboxes]

I ask because I've got a mail server system I'm happy with, but just want to bolt a better anti-spam filtering system on in front of it.

Thanks.