How do I make an automatic email notification when I tag a contact?
Set up the tag in question as a tag goal in the campaign builder. Add a sequence behind it. In that sequence, add an email and it will send an email the first time that tag is applied.
To expand slightly to Jeffs answer, at the top of the email builder, look for the To: line and you can update that to any email address you want.
Important: Make sure the email address you are sending the notifications to is an opted in contact in your contacts list