#3: Evaluate Your Content & Messaging
The final piece of the puzzle comes down to content, and handling the expectations of your subscribers.
a. Set clear expectations
One of the easiest things you can do is include a welcome email with "what to expect" and how to whitelist you to ensure they don't miss anything that they're expecting. Also, be sure to let them know how to update their preferences at any time. In fact, this is a good idea to include in the footer of all of your messages.
b. Test Content and Timing
Email marketing is always changing. What used to work a year ago may no longer be effective today. It's important to test the frequency of your email messages as well as the timing.
Also consider your messaging and stick with what you promised in the beginning. If your business has expanded, then INVITE subscribers to join additional lists to receive the new types of emails.
c. Review, Evaluate and Modify
Watch your bounces on a regular basis to gain more intelligence into your email program, to see what people are responding to, and to find out what's causing people to leave your lists.
You want to keep your bad addresses (hard bounces) to a minimum (less than 3%) and carefully watch soft bounces to remove full mailboxes after a max of 7 attempts and to manage content-related bounces and spam complaints.
Keep your complaints to a minimum. A general rule of thumb is to keep your complaints under 0.01% and to immediately put them on your do not contact list. This ensures they don't resubscribe and complain again.
High complaints will also cause the ISPs to filter your email messages to the junk folder, and may make it very difficult to get your campaigns BACK to the inbox if the problem persists for a long time.
Watch unsubscribes regularly to evaluate the types of content that causes spikes in complaint rates as well as problems with individual campaigns and autoresponder messages.