Lost in the 9 Circles

I'm the executive director of an educational nonprofit. We send out our constant contact everyone two weeks with featured products and upcoming events that people can register for. Our open and click rates are fairly good - but when I'm thinking of segmentation I'm lost and overwhelmed. I have 52 other hats to wear and our enrollment data doesn't show if someone is from lending, a retail branch, back office, etc. We have names (thousands) and email addresses - that's it. I can't see me going through the entire list and researching over 2000 names to put them in a segment. Any direction I should take?

One thing that happens is that people say they get too many emails from us. Not sure how that happens when they get 2 a month. Research is showing that other organizations like ours are emailing like 10 times a day. How do you manage your brand reputation and still communicate?

I recently worked with Constant Contact and got a brand new design on our email newsletters that will launch in September. Looking forward to seeing how the new look and feel will work. 

Anyway - any thoughts on segmentation when marketing is only one of your jobs at a small nonprofit and how to protect your brand when others are emailing newsletters multiple times a day and people think it is you.