For data to be effective it must be relevant, accurate and current. The most significant benefit of email marketing is that there is no other method of marketing where the three requirements are satisfied so completely. So it might seem a little odd to suggest you should try other ways of obtaining data.
There is a considerable amount of literature available, such as newspapers, magazines, including those specific to your business, annual reports from competitors and reports from regulatory bodies. But, of course, such material is bound to be old, if not out of date, and is available easily to your opposition.
Taking the last point first, there is a big difference between being available and being researched. It is possible that your competitors will not read beyond the headline of wordy reports in Email Marketing Monthly. After all, it is a bit of an effort. But that means those who do have an advantage.
Don't ignore these alternative sources of information, although always bear in mind that the printing and publishing process means it might be, at best, a couple of months old.
There is data out there that is updated in real time. It is, remarkably, ignored by many because it is seen as chattering, which is probably a fairly accurate description, although talking to individual customers about their needs is an expensive but valuable way of obtaining relevant information.
Internet forums are hardly new and that might be one reason they are ignored. However, as a source of information and opinion, they are just about as current as it gets. A little research on a macramé forum will identify to any material supplier the problems the knotters are experiencing when searching for specific cords. If you provide a source, the members will advertise your products for you.
Then there are other forms of social media. Facebook and its clones are an unending, very much so, source of information for anyone willing to take the trouble to log on.
Researching online has the distinct advantage of being free. It will tell you what problems your potential customers are experiencing, what they need and what the Subject Line for your next email marketing campaign should be.