Most of the emails from my mail server are going into SPAM on gmail

This has been happening a lot lately. When I send an email to someone with a gmail account it invariably goes into their SPAM. I tried this with a never-used gmail account of mine, sending from my own mail server novatec-inc.com, and it too went into SPAM. The reason given by gmail was, "Why is this message in spam? It is similar to messages that were identified as spam in the past." To whose "past" are they referring? Certainly not mine as this is the first email I've sent to that gmail account. I've posted a 'Support' message from my gmail account asking what the problem might be, but I've received no answer, and don't expect to.

Does anyone have any idea what I could look for to figure out why gmail considers me to be a SPAMmer? I need to sort this out because email is how I communicate to everyone, family, friends and customers.