Everyone hates getting spam e-mails, but if you use Outlook, you can block a sender so they can never contact you again.
How to block a sender in Outlook
In Outlook, right click on the offending e-mail, scroll down and look for the Junk menu, then click Block Sender.
This will not only block that address from sending to you in Outlook, but it will also tell Office 365 that the message is Spam and block it system-wide.
How to do it in Outlook Web App
If you use the Outlook Web App, the process is a little different.
Click on the offending message and click the more button in the top right of the message itself. Select Mark as Junk which will move this message to the junk folder.
To block the sender completely, click the Settings menu in the top right corner. Then click Options. Click the block or allow menu on the left and scroll down to the blocked senders list. Here you can type in the address or domain you wish to block, click the plus sign to add them, then click Save.