In Outlook, you can ignore unwanted email conversations, including reply all messages. To do this, first open Outlook. Then navigate to the message you wish to ignore. Click the Home Tab, then click Ignore beside the large Delete button. This button moves current and future messages in the selected conversations to the deleted items folder. Alternatively, navigate to the message then use CTRL + D. Both options move current and future messages from this conversation to the deleted items folder.
In Outlook Web App, right click on the email message you wish to ignore then select Ignore Conversation. The dialogue box will prompt you. Select OK. That email chain will now go directly to the Deleted Items folder with every new email.
Knowledgebase Article: http://helpdesk.etown.edu/helpconsole2012/KB/default.aspx?pageid=ignore_email_conversations