An example that comes to mind is postfix (the SMTP daemon). It hasn't had zero memory safety issues, but nearly so. Certainly an abnormally low amount given the size/complexity of the project and the number of eyes on it.

It's also had a pretty 'normal' (read: higher) amount of non-memory related bugs such as SMTP smuggling of filesystem permission TOCTOU, so it's not like its devs are somehow really good at just not writing bugs.

Maybe they have chosen a software architecture that allows them to avoid complicated memory-related logic? I genuinely don't know, would love to hear from a postfix developer.