Hmm I think this is something that we’ll not integrate directly into InvoicePlane as it’s not related to the main functions.
But we’re planning an API for InvoicePlane v2 so you will be able to connect services like Mailchimp or other open source Newsletter apps to InvoicePlane.
Great Idea. I think the API would be great to have. Looking at integrating the IP to client’s real-time service based platform where service delivery is dependent on having paid for subscription. Such services like CableTV subscription or broadband Internet subscription.