Ignoring a Conversation Thread in Web Outlook
A conversation thread in the Outlook Web App is any response to an original email. When you ignore a conversation thread in Outlook Web App, you remove and ignore any future responses.
To ignore a conversation thread in Outlook Web App, find the email conversation to ignore in the Inbox pane. Right-click the email message and choose Ignore from the list of options.
When you click Ignore, a pop-up box appear warning you that all messages from this conversation will be deleted from all folders.
The only exception is the Sent Items folder. No messages in the Sent Items folder will be deleted.