If all you have is the email address of your client, and you would like to add fields to your subscription form, you can do so, that way, when your clients click on “Update Profile” on the footer of your email, or in the subscription form in your website, you can certainly have them update their profile with more information. You can add many fields including topic of interest, that way they can choose from a variety of topics that you offer them.
There is nothing that clients hate more than to constantly receive information on themes that they are not interested. That is why it is so important to get to know your clients preferences.
If you send information to your clients, and they are not interested in receiving regarding that subject, chances are they will lose interest in your company, and one day not too far, they will completely stop opening your emails, that is why it is so important to segment your clients by their topics of interest.
You will see that your clients response rate increases when the information you send them actually matches what they said they were expecting to receive from you, in the subscription form, or even in their profile.