You must discover what your competitors and others engaged in email marketing are doing. You will be pleased to know that there is no need for expensive and illegal industrial espionage. All you have to do is subscribe to a few email lists.
Create a number of email addresses to keep specifically for research purposes. Use one when subscribing to your competitors’ email lists, another for those you believe to be the leaders in a different form of email marketing and also one where you have ticked the box to allow your email address to be shared with other companies. You can then sit back and await masses of information.
If you are concerned about the number of blocked emails you are experiencing then you should examine those that fall into the spam folder of these addresses. You’ll find they will have features in common with one another and, perhaps helpfully, items which they share with your blocked emails. This will tell you quite clearly what you should avoid. But don’t ignore those emails which sailed through as you have as much to learn from good practice as bad.
Emails you receive from the leaders who are not your competitors will show good practice. Compare them with those from the companies who market the same product as you. If there is some specific feature, a clever little procedure, which neither you nor they are using then the design of your next email has been partially decided.
When you tick the box to allow your email address to be shared with other companies you can be certain of a full inbox. You might feel that you will have little to learn from such companies and you may well be right. However, many of these might be new to the craft and could well discover some clever approach that those who are more established have missed.
There is no charge, apart from time, but it is a continuing exercise. Spam filters evolve with time and at speed. When a competitor suddenly changes a feature, you must work out why. Knowing what your competitors are doing is halfway to beating them.