I would personally put bullet points grouping your skills together like this:
- HTML, CSS, Media Queries, Ghost Tables,
- Litmus, EmailOnAcid
- MailChimp, Constant Contact, Campaigner, AWeber
I would list any skillset that you have and add them together.
Don’t forget to add your JavaScript or E-mail Framework skills if you have any.
WHAT TO PUT IN THE TECHNICAL SECTION OF YOUR E-MAIL DEVELOPER RESUME?