[rapht]

My understanding was that the main interest of SendGrid, Mailgun et al was precisely that they manage to (more or less) reliably mass send email through the great MS/Google/Proofpoint, where hitting the recipient's mailbox is less than guaranteed if you self-host.

[wildekek]

Maintaining sender reputation is tough and I don't think anyone in their right mind should try this in house. If you're not a M3AAWG member, you'll probably hit a brick wall when trying to explain to Google why your whole IPV4 block is erroneously on a blocklist.