Notice the asymmetries in work, you send an automated mail with zero load for you, and, interested or not, the user should have to read all your mail, and decide that there is even more work to do if he wants to reply. You have minimum effort in one side, maximum in the paying other. With a short mail at least the reading work is not so bad, but you still have the analysis one.

But giving out information that should matter to your particular client, like personalized info on how things are for his user (like how his account is using the service provided, and some hints on how to improve on that with new offerings) may deserve some more thought, even if that report/mail was generated by an script. Give more effort to your side. Even if is longer or require more work for the end user.