In this article Spencer Kollas breaks down email success explaining that domains are the first step.
A domain analysis is the first step to ensuring your email messages are delivered as intended. A few domains dominate the market, but your audience's usage could vary, so it's important to run a report to see exactly which domains are represented in your databases. Consumer lists are likely to be dominated by AOL, Yahoo!, MSN/Hotmail, while business lists may also contain large company domains.
Next, you'll want to assess how your content appears in each domain, and whether or not you have some ISPs where your message is breaking or images are missing. Using one of the many email rendering tools available is an important step to understanding how your brand and your messages are being presented to your customers. Analyzing reports that show previous campaign results by your top domains can allow you to compare metrics such as open rates and clickthrough rates to see if there are any potential issues as well. Once you've identified the domains delivering less-than-satisfactory results, you're ready to tackle each one's specific deliverability barriers.
Read the article and find out what are the main do's and don'ts of domain analysis (according to Spencer Kollas).