To get the benefits from your email marketing software you must ensure that the data the calculations are based on is as good as you can get. If you are going to invest money and other resources into a marketing campaign you will want the statistics you base your assessment of it on to be accurate.
Everyone on your email lists is not the same. You will probably have already moved high value customers onto their own email list to ensure you look after them. This also means that one large purchase does not distort the stats. The same should go for those at the other end of the spectrum. Those who are dormant. Putting them on a separate email list gives two main benefits. Firstly the statistics are more precise and secondly you can try and make them active.
There are inherent dangers to allowing dormant subscribers to remain on your email lists over and above distorting returns. It is a fact of email marketing: if they continually fail to open the email, delete or, worse still, mark it as spam it can cause deliverability difficulties. What makes a subscriber dormant will depend a great deal on the frequency and value of your email marketing. It is probable that the definition would change over time.
Once the dormant are on the specific email list you must try and find some common factor, something which makes them react uniformly. For instance, are the majority or a substantial number from one particular country with no other common demographic? If so then you should check with your main email list to see if there is a difference between that group and the dormant one. Such comparisons are easy enough with free email marketing software.
It could be that you're not connecting with an age group, women or those with money to spare. If the majority of that specific nationality are dormant then you should check that local traditions are being honoured and that your translator is up to the job. It might be something quite simple. How were the addresses collected?
Perhaps you offered a free gift at a trade fair for any who subscribed to your email lists. Consider if the value of the gift was too much of a temptation. The joy of having an email list that consists of dormant subscribers is that you have little to lose by experimenting with them. Once you have established a common factor among some of them these should be separated. This is where the fun starts. You might think it possible that local traditions dictate that email marketing is a bad idea on a certain day. You can quite easily split your email list into two and see if there is a significant difference. Your email marketing service will make this clear.
Getting subscribers to your email lists isn't the be all and end all of email marketing. A dormant subscriber is of no use to anyone. It takes little effort to target them and to give yourself a chance of turning them active. What have you got to lose?