When I tried the link posted above yesterday, I was also "sent" to the main Apple Support page. To work around that I copied the HT202235 and then searched for "Apple Support HT202235", which then brought up a link that when clicked went directly to the article "How to delete apps on your Mac".
As for deleting apps that are "embedded" in macOS, seems like more trouble than its worth unless one wants to use the reinstalling macOS as a learning experience. The main concern as I understand it is to reduce the storage space that email is consuming. Mail is just pulling down email contents from the mail service provider(s) and storing it locally.
So, if the goal is to reduce storage space used by the Mail app going forward; perhaps configuring Mail to not download email is an option. Alternatively, email could be accessed via a web browser if the email provider supports that option.
Also, make sure you have a backup for all currently downloaded email, or a way to access it online via web browser if you use IMAP and have configured your email to keep a copy on the mail server.
Another option could be to Archive email
https://support.apple.com/guide/mail...-mail35918/mac and store externally.
When searching for "archive macos email store on external drive" some articles appear, with one being
https://discussions.apple.com/thread/6488557 While for an older OS version, details may be relevant. There are newer articles surfaced from the search above which may help.