If you and I are both using SES to send to the same person, and my message results in a hard bounce, then your messages to that person will start to silently fail.
[1] https://docs.aws.amazon.com/ses/latest/dg/sending-email-glob...
> If an address is on the global suppression list, but not on your account level suppression list (which means you want to send to it), and you do send to it, Amazon SES will still attempt delivery, but if it bounces, the bounce will affect your own reputation
[1] https://docs.aws.amazon.com/ses/latest/dg/lists-and-subscrip...
If I had to rely on email for critical comms, I would use a product that lets me see the SMTP logs, and alert on failures. I would have some backup provider that I could then quickly shift to
But I'm still an on-prem email administrator, so my entire paradigm is pretty much obsolete. I may not be the best source of info in this space