Do you email your customers only with discounts? Are you testing email strategies? How clean are your lists? These are just a handful of the questions addressed in today’s “Increasing Your Email Inbox ROI.” The panel, which included marketing execs from Harry & David, Williams-Sonoma, Overstock.com, Charming Shoppes and Return Path, offered seven ways to increase your ROI:

1. Listen to your customers. Customers are quick to block out retailers, so make sure that you are actively engaging them with email. Try hosting a poll, adjusting the frequency of your messages or see if you can help subscribers network amongst themselves.

2. Get relevancy right through testing. Try different types of subject lines or target customers using segmentation. Whatever you do, make sure you have a way to measure the success of the test.

3. Grow a profitable list, not just a large one. Be clear at the sign-up stage about what you will be offering customers and state all the benefits. Include sign-up forms everywhere you can. Also, if you have bricks-and-mortar stores, make sure employees are capturing email addresses there too.

4. Break through the clutter of the Web 2.0 world. There are tons of Web 2.0 opportunities for Web marketers. Use Facebook or other social networks to invite customers to subscribe. Maximize your use of blogs. And remember the power of video.

5. Measure the right things. Make sure you’re measuring the right metrics. Some specifics to look out for? Click-through rates, click to open rates, subscribe and unsubscribe rates, bounce rates and conversion rates, to name only a few.

6. Reach the inbox. A good reputation is invaluable. Make sure your file is clean, that way you don’t risk emailing people who don’t want messages and may label you as spam. You want to keep complaints to a minimum.

7. Keep the offer fresh. Test triggered messages after a purchase is made or if there has been a lapse in activity. Make sure you’re sending relevant messages at timely intervals — but don’t overdo it.