gmakhs PMG requires manual configuration. You would need to add each domain you want PMG to relay email for. For mail to be accepted at the receiving server you also need to configure DKIM, SPF and DMARC.
My personal opinion is that if you got a mission critical e-mail setup, as in right now, go for PMG (as a temporary solution). If you can afford waiting for Enhance to expand their spam controls - or if you don't already struggle with excessive spam - wait a few months for the updates. PMG will add manual labor for each added customer domain, and extra complexity to your stack. You would also need a good understanding of how e-mail works.
