Optimizing the number of recipients who open your email is all about list quality, segmenting and targeting audience, your brand trust, and writing really good subject lines.
Keep in mind that over half of emails delivered are now being read on mobile devices. So, be obsessive about your "from", "subject", and "opening paragraph". Make sure they are mobile friendly.
The most important factor in opening any email is the senders name. Your brand reputation is therefore one of the most critical factors to protect. And the best way to build a strong and lasting brand relationship is by providing genuine value - segment your audience and make sure you don't send irrelevant content.