1. The reason guesser
His goldfish died while the customer was installing your software. So it must be your fault. That’s why he sends you a three-page e-mail.
2. The ignorer
You wrote that the customer should do 1. … 2. … 3. … to solve the problem. The customer writes back that he did something completely different, that it still doesn’t work and that your support sucks.
3. The insister
Tells you that you’re all wrong, ignores everything that you wrote and insists that you’d better send him a solution RIGHT NOW.
And probably there are many more types…