Upgrading subscription plans requires agreement to specific terms of service, collection of an e-signature, and confirmation email sent to the customer and shop managers.
Using Contact Form 7, we hooked into the form submission to submit the relevant form fields directly to MailJet via their transactional API. We then merge that data into a template built using MailJet's drag and drop editor.
The upgrade information, as well as the image of the client's signature, are all sent to the API where the data is merged into the upgrade receipt template to render a beautiful, mobile-responsive upgrade receipt transactional email.
Separating the email design from the data processing code allows the client future access to the design of the email without having to wade into any actual code.