Mentor Group Gold
Why not setup your own multiple-IP mail server - with the correct DMARC, DKIM and SPF records. We use a service called easydmarc to monitor and manage our mail systems.
Last year we had a really knowledgeable guy from OCT to help us with hints about how to get rid of the DDOS attack we were under, he knew a lot and also told us that we had to avoid mail services that reveal our servers IP address when we send out emails (it was in the email header). That is what Mailjet does, they don't reveal our IP.