Why do you want to send a message showing that spam has arrived?

1. mail filter: Your email provider or email client will automatically mark some emails as spam and put them into the spam folder. This is achieved by detecting possible spam marks in e-mail content. Sometimes, normal information will be wrongly marked as spam.

2. Reputation of the sender: Some mail providers or security service providers will maintain blacklists and whitelists to track spam and trusted mail. If senders are blacklisted, their messages will be treated as spam and sent to the spam folder.

3. Content filtering rules: Set content filtering rules on the mail server or email client to detect and prevent the sending of spam. These rules will be judged according to specific keywords, URL links, attachment types, etc. , and mark the matching email as spam.