Open a message from the sender, open the message's More menu, and choose Block.
Step by Step
- Open Gmail and open a message from the sender.
- Open the More menu for that message.
- Choose Block followed by the sender's name.
- Confirm if Gmail asks you to.
- Future messages from that sender should be directed to Spam.
If That Doesn't Work
- Blocking is not the same as unsubscribing from a legitimate mailing list.
- For persistent abusive or fraudulent messages, use Gmail's spam/phishing reporting options as appropriate.