Hey amd really sorry about that, we'll look into how that happened. We had a spam issue on the forum recently and it's possible your email was wrongly caught up in that.
Good news on the 'internal links' question, you have a few options:
1) The page outline: In the top-right of every page, you'll see a page outline by default. This will show a clickable list of the different headings on that page (paid plans can customise whether this shows)
2) Manually add links: If you hover over a heading you'll see a copy link icon appear to the right of the page. If you grab this URL you can paste that into your documentation.
3) More link options: Not exactly what you asked but might be helpful to know — there are more options for adding links to documentation, including shortcut tiles and image links, explained here: https://learninghub.zeroheight.com/hc/en-us/articles/4948435619227-Add-links
