Much of the spam sent to my business' email address doesn't even have an automated unsubscribe capability. The unsubscribe link is just a mailto: address, which

Much of the spam sent to my business' email address doesn't even have an automated unsubscribe capability. The unsubscribe link is just a mailto: address, which I am convinced these shady operators use to indicate the mailbox is being watched and, thus, a good target for future mailings. They go right into Fastmail spam and are scored accordingly.