It is pretty much unacceptable to have a domain bouncing emails, so I’d be out of the provider before the MX TTL even expires.

For outgoing emails, reputation is a huge issue, but at the same time it’s also fairly trivial to set up a (different) 3rd-party (gmail, outlook, sendgrid, whatever) with previous reputation so you can get back communicating.

I'm not running a spam business. I've been operating my own mailservers (and related infrastructure) for more than 25 years now, without issues.