I'd like to apply for a job in a different field from mine. I have a lot of skills that would transfer across but one of the essential criteria listed is a knowledge and experience of a certain type of software. I have never used anything like it before but I would certainly be capable of learning.
Is it worth at least approaching the person given as the informal contact? How would I word an email? 'Hi, I'd like to apply for your job but I don't have this thing you've asked for' seems a bit wet.