Based on all the information we have gathered during our in-depth research we assign a magic score to each vendor. This is based on factors that affect any solo ad purchase (for e.g: CPC, Sales, Conversion rate etc). We use our proprietary algorithm to do this. As a rule of thumb, higher the Magic Score, better the solo ad experience is going to be.

This A/B test indicates that engagement is one problem, but your subject lines are an even bigger problem—and one you can solve right away. CTR rates are understandably lower among the less-engaged group, but you saw engagement increase with a punchier subject line, so there is room to improve CTR among cold leads. CTR rates are higher in the more engaged group, but with a better subject line, this rate could go through the roof.
When you want to create a win-back campaign: Develop a series of win-back emails to encourage inactive subscribers to re-engage, and utilize post-sending actions to automatically perform a specific list action on subscribers after they receive the final email in the series. This could be used to update one of their merge fields, move those subscribers to a different interest group, or to remove them from your list completely.
Part of the problem is that people are confused about the difference between ‘strategy' and ‘tactics'. It's essential not to get these two confused. They are related – tactics are a vital part of what makes a strategy work – but they’re not the "be all and end all." Too many people neglect a full and comprehensive strategy in favour of a bunch of loosely-connected tactics. So, to recap:
Genuinely effective campaigns segment the market as carefully as possible, and target accordingly. Relevancy is key for getting people to open emails and respond to your CTA – but what's ‘relevant' differs from person to person. If you're going to make your emails as relevant as possible to everyone who reads them, you need to Segment, Target, and Position.

Everyone's busy and their inbox is already full. Why add to the problem with a longwinded email? People generally like short, concise emails better than long ones because concise emails have an obvious focus. Plus, when your users are scanning through all their emails in a short amount of time, they're more likely to find the overall message before deciding to take any action.