If you receive unwanted email in your Inbox, you can block it with Filter Rules. Messages flagged as spam will go to the Webmail Spam folder. Your only option to stop them is to "unsubscribe". I was suspicious of doing that, but my primary account was getting 60+ spam messages per day so I decided to try it. Spam has since decreased to maybe 1 or 2 per day, often none.
The "Controlling the Assault of Non-Solicited Pornography And Marketing Act of 2003" (Can-Spam Act) requires that all commercial email contain an obvious link to opt-out from future email. Any opt-out offer must be able to process requests for at least 30 days after the message is sent. This request must be honored within 10 business days. Companies may not charge a fee, ask for any additional personal information or sell email addresses in the future. A company that disobeys these regulations can be subject to steep fines.
However, clicking an "unsubscribe" link comes with risks for various phishing and malware attacks. You could be confirming an active email address that could be sold to cyber criminals. Don't click "unsubscribe" if the link is a tiny URL. Outlook will give a warning message. I don't know that Webmail does that, but you can copy the link and check it before you click it. Don't click "unsubscribe" if the email looks suspicious. A legitimate company's email probably won't have misspelled words, poor grammar or a generic domain like gmail or hotmail. A non-generic email domain doesn't guarantee the link is safe either though.
The above describes the only option to block Webmail flagged as spam, my own experience, and potential risks. Decide for yourself when to "unsubscribe" from Webmail going to Spam.
