There are a few different things that can impact your open rate. The goal is simple—to get your reader to CHOOSE to open your email (and especially in a crowded inbox, to open your email over another).

First off, make sure you’re building a real relationship with your membership.  If your emails are worthwhile, with a consistent style and voice, members will get to know you, understand that what you send to them is important, and will open it just because it came from you.

Next, the subject line of the email is important.  Being brief and direct is key. You don’t have to get the entire message of the email in the subject—you want to entice them to open and read more.   For instance, humor or a provocative topic can work as a subject, as can a subject that asks a question (the simpler the better).    Including the name of the recipient in the subject (ex. Jane, we need to hear from you), or an unexpected combination items (“Polar Bears, Solar Panels and Apple Pie”) can grab a readers attention as they scan the inbox.  Use action oriented language that conveys the urgency of message, but don’t exaggerate.  If a situation is life or death every time you send an email, you risk diminishing your open rates in the long term.  

Test the performance of your subject lines to see what resonates with your members and to compare open rates (and folks who actually took the action).  In fact, consider testing a couple of subject lines for one email—if you have a few subjects that you like, use them all to see which ones work best.

The sender of the email (the person on the From line) also influences the voice for the messages you send – and your open rates. Using the same sender every time can help to build a relationship, or you can use a celebrity or a notable expert for a particular issue or campaign.  This can grab a reader’s attention and provide a bump in open rates for a specific email.

The timing of an email can also play a roll in open rates.  Data shows that emails sent in the afternoon don’t do as well as emails sent earlier in the day.  The day of the week doesn’t have as much of an impact, but weekdays tend to perform better than weekends.  Emails sent during holidays don’t perform as well as ones sent on non-holidays.    
- Clarissa Goodlett, Color of Change www.colorofchange.org