BoltMail
Can I subscribe a user to many contact lists at once?
Yes. A subscription form can be used to subscribe your visitors to multiple lists by filling out the one form.

When creating your subscription form you can select which contact lists to allow users to sign up to. They will then be presented with a list of checkboxes that they can select from to sign up to each list.

If you'd like to not give them the option but instead force them to be subscribed to multiple lists, you'll need to change the check boxes to hidden fields in your HTML code.