Exporting HTML code from Email Template wont work with affiliates ESP

An affiliate organization that sends a monthly email out for us uses as ESP that wont work with the Marketo HTML because it uses meta tags rather than incorporating them into the css. That being said, the organization uses an old esp “listserv maestro”

I am very new to a lot of this but figured I would ask. Creating emails in Marketo and being able to export them for other organizations to send for us, self-sufficiently, is a high priority for us going forward. Would anyone be able to help with this or do we need someone to manually build out these emails?

Thanks