So my client had a recent problem with their mail server not receiving any emails. It was apparently an issue with their self-signed certificate expiring almost 3 years ago. I have no idea how they didn't notice it for 3 years. So if you're running a mail server and it's advertising that it supports STARTTLS, make sure you check your certificates.
Anyway here's what we went through:
So I get an initial call last Thursday morning. Basically a client has called and asking me for help. Their email server has not been able to receive any ...