We have one client who enjoys a 50% open rate for the monthly email we send to their clients.
The main reasons for this are:
1 The email looks nice. It's well designed and has short punchy new items with lots of nice images.
2 The email contains a very good offer, i.e money off vouchers.
3 We send the email out to a very targeted list of customers who have requested the email.
If you follow these rules, then email marketing can be one of the most effective ways to communicate with your customers.