In the world of email marketing, there is several things that are in play and you always want to make sure to avoid "list fatigue". The overriding goal should always be to increase subscribers, which in turn will increase customers (or students) if you are in higher education.
Here are some practical tips to email market well and avoid list fatigue. First, focus on the subject line and make sure it is attention getting, your email has the best chance to be deleted at this point.
Next, make unsubscribing easy, because if someone is just not interested, you do not want to pester them with emails and frustration can set in from unsubscribing. I think word will get around quick, or it could be talked about in social media!
Do watch your quantity of emails, people will tire if they are receiving an email every single day, best to do once a week.
I think the most important thing to do is always provide fresh content. The information should contain something new and educational to the reader, promotions are fine occasionally, but be careful of doing this too often.
Lastly, do not use email marketing only. For example some magazines solicit email addresses via postcards and consumers or students can fill the postcards out and return them to the school or business. Another avenue to think about would be sending out a letter as a invitation to fill out an electronic card online. If you can combine these with a successful marketing campaign, you are well on your way!