If you have items in your object lists that you never look at (for example a Conversation that doesn't apply to you), or you're seeing updates in your recent activities or in your email digests about items you don't care about, you can mute those items. Muting an item hides it and its activity from your view. It's still there; you just won't hear about it anymore. (The only exception is if you're flagged on a message in a muted item, for which you will still be alerted by email based on your notification settings.)
To mute a Conversation, click , then select Mute Conversation.
To unmute a Conversation, from the navigation menu, select Conversations. In the Show menu, select Muted, then open the Conversation. Click , then select Unmute Conversation
For more information, see How do I mute or unmute an item?