How can you attract new donors online? Here are four tips for using email to acquire new donors and build relationships with existing donors.Collect email addresses.Most people probably won’t make a donation on their first visit to your site, but if you get their email addresses, you can start building a relationship and invite them back to your website. There are many ways to collect email addresses, such as offering an e-newsletter or inviting people to sign an online petition.Make it easy to subscribe.Carve out space above the fold on your home page to promote your email newsletters. Put a box for capturing email addresses in a prominent place throughout your site.Make your messaging interactive.Create compelling calls to action and special offers. Let recipients interact with your content. Build simple interactive polls and fundraising challenges and watch your response rates and donor data levels climb. Remember, a two way relationship is harder to break than a one way relationship. And don’t forget to include your donate now button.Keep your subject line short & sweet.When it comes to email marketing, the best subject lines tell what’s inside, and the worst subject lines sell what’s inside. A recent study showed that subject lines with 49 or fewer characters had open rates and click-through rates up to 75% higher than for those with 50 or more characters.