Hi, there are multiple reasons this can't be done:
- Client support for form inputs within HTML emails is so spotty as to make it unsuitable for any audience except an internal one (where it's literally your employees receiving the emails and you tightly control the supported software).
- Even in the rare case when it's supported, it's an unfamiliar experience, violating the principle of least surprise.
- Mail scanners pre-click links in your emails to determine if they're malicious. This means the forms will be auto-submitted by those scanners (albeit without any data filled in).
- While it's possible to create fallback content that (for the most part) will display in lieu of the form when the mail client is known to not support forms — i.e. a traditional button linking to your LP — you'll spend so much time testing that fallback logic that you'll have negative ROI.
In sum, this isn't practical in the real world. Use a traditional Landing Page w/form, so it'll have acceptable support and only be submitted by actual humans.