People bring up postfix all the time in this context because supposedly nobody has ever found a memory safety vulnerability in it. Presumably this is supposed to make the point that it is possible to write complex programs in C safely.

The reason people know this about postfix and keep bringing this one specific example up is because it's so unusual! It's an example that almost stands alone, it's extraordinary.

I don't think this is making the point about the safety of C that you think it is.

There is a mountain of evidence suggesting that C is dangerous, particularly for network services, and one possible example to the contrary doesn't change that.