[truekonrads]

Deliver via sendgrid*, receive directly is probably the only viable path for self hosted systems.

Where sendgrid=any major player, could be Mimecast, proofpoint or anyone else who will forward outgoing email.

[dpifke]

FWIW, a huge percentage of the spam I get is via Sendgrid, and at some point in the past year or two their abuse reporting mechanisms all turned into black holes, so mail sent via Sendgrid is heavily penalized in my spam rules.

Sending reputation is just as applicable if you're using a third party as if you're hosting it yourself, but much less under your control.