Add new members to 2 mailchimp lists using the build-in ping

Hi,

I have 2 lists in Mailchimp that new members on my site need to be added to:

1. A series of drip emails that show them how to use their membership to my site

2. A general mailing list that I use to send mass emails/newsletters

Right now I have used the ping system to automatically add new users to the drip. How can I also automatically add them to the mass email list when they sign up?

Thanks!