Use rules instead of smart mailboxes.
While your Inbox is highlighted in the side bar, head to:
Mailboxes - New Mailbox - Location: On My Mac - Ex: Amazon
Then when you get an email from Amazon - highlight the email and head for:
Preferences - Rules - Add Rule - I name the rule same as the Mailbox created above.
It should look like the below - if the email you want to create the rule for is highlighted, when you change the "to" to "from" the from address is automatically added for you.
Now all receipts, bills, invoices, spam or whatever are all in one place and will no longer clutter your inbox nor get deleted by mistake.
This is also an excellent way of dealing with email from places (like Amazon) that sends out a lot of spam which you don't necessarily want to see all of it, but you don't want to unsubscribe from either.
As you see below I have an Amazon subfolder for their receipts - so all the adverts (spam) go in the main mailbox while all their receipts go in the receipts folder.
Some places, like Amazon, have multiple email addresses used.
After you've created the rule and you receive a 2nd email that should go in that Mailbox - highlight it - head back to Preferences - Rules - highlight the Amazon rule and choose Edit. That will auto add the highlighted email to the rule.
Remember, you need to create the Mailbox before you create the rule.