According to HubSpot Academy, this is the scope of the material for the Email Certification:
The certification is suitable for designers with experience in crafting website pages, templates, and styles. Basic proficiency in writing HTML and CSS are required for completion. This two-part certification will test your proficiency with using HubSpot tools to design.
My certification was valid until October 2017, but I’ve been a practitioner and led teams who practice this discipline since.