Ghost newsletter mail for any email service integration

Hello,

In Ghost for newsletter/bulk-mail service Mailgun is default integration, it has their benefits, ghost is tightly coupled and built features based on it and we respect that.

Currently available alternative options to send email are through web-hooks or zapier integration. Well i have tried both and In both the email are lost its UI/styles/css. I have reviewed bulk email lib and mobiledoc but no clue to get thing done.

How can I achieve newsletter template UI with my own web-hook to send email?