We use Amazon Simple Email Service for mail. It’s very low cost (of the order of a dollar a month), and allows 50,000 emails per day. Recently perfectly legitimate mail from out site is being classified as spam from Amazon SES, and so not reaching recipients (including me) and bouncing. I do not comprehend this as Amazon SES has a very very high email reputation (reputation is a technical property, not just an adjective). There appears to be nothing I can do about this.
Clearly this mail will not be received by the very people that are affected - it’s not all users. But I am putting the message here so that at least when people use the web they can be aware of the issue.
I am not sure how to solve this, and it’s difficult to get support for the free tier of Amazon Web Services products,