Is custom HTML shown in email newsletter?

I’m scraping some websites and producing some output HTML.

I’m using the HTML card in the editor.

The output HTML is shown in a bunch of lists, with icons aligned to the left.

The preview for that page looks ok in the website preview.

Two questions:

First question
I’m understanding now that there are no custom email templates.

Does that include the HTML I’ve inserted via the HTML card? Will this not show up in the email version of a post?

Second question
How can I preview the email locally? Do I have to set up SMTP locally and send myself a newsletter? Is there any option to preview it (the newsletter version) WITHOUT sending myself a newsletter?