I love the email forwarding feature, I use it daily. You want someone to add notes that can't remember the syntax for notebook, they get frustrated and start to hate you for making them do this In the case of a misspelling/typo (or autocorrect on a phone) note goes somewhere else
This is not possible with auto-forwarding filters in Gmail or other email providers I know it's supposedly easy to add to the end of of subject.
I know, it is possible to route an email into a specific notebook by adding to the email subject but in practice, this is inconvenient, time consuming, and error prone. I am suggesting to have a separate email address for each notebook, just like Todoist has a separate email for each project. Currently, all emails I send to my Evernote "Email Notes to" address land in the "Inbox" notebook.