I have a mail slot in my garage door. For anything larger, my mailman has it held at the local post office till I get back.
By the way, I don’t tell my neighbors if I’m going away. I live in a rough neighborhood. They might be the ones who would break in. Only my brother and a few trusted friends know when I’m away.
My brother, who used to work for the Post Office, told me that new mail slots are not permitted, old ones are grandfathered in. The ostensible reason to prevent injuries to letter carriers, the actual reason is because the post office could not compete with bulk carriers.