It sounds like you are where I was twenty five years ago. You have some interest and enthusiasm and maybe a certain knack. You are probably a local expert, the guy other teachers turn to when they get frustrated with technology. A career in IT -- that's what you are describing when you say you want to set up email servers -- sounds like more fun and money then teaching.
But, unless your "knack" is a true gift and you are willing and able to put all your mental power into acquiring the deep knowledge you will need to operate at a high level in your new profession you will end up frustrated, stressed, and frequently out of work.
I.T. is a dead end. Fewer and fewer mid-level jobs; more and more automation, consolidation, and out-sourcing.
And believe me, you don't want to be crawling under desks and tracing network connections when you are fifty.
Or maybe you do. My 2 cents. Good luck to you.