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