[sethammons]

Have you ever thought, "huh, my {confirmation, receipt, password change request, etc} email never got here" for this site or service you either use or tried to use? If so, they were likely a customer of an ESP you blocked.

[inferiorhuman]

Nope -- in terms of folks I do business with or have accounts with Marketo, Mailchimp, and Sendgrid are only used for marketing nonsense I don't want.

Self-hosting my mail stuff means I'd see if I were bouncing legit email pretty easily.