There may be some scenarios where you do not want a channel's contacts to receive an email notification when you send a new message in the channel:
Adding files to a channel as they're ready but do not want to notify your client yet (ie. compiling files for a tax return package for a client)
Uploading files to a channel that do not require the attention of other channel contacts
For these scenarios like these, the Send notification toggle will allow you to control whether or not contacts will receive an email notification.
The Send notification toggle appears at the top right corner of the message box.
By default, the Send notification toggle will be set to ON (green). When you click on the toggle, it will turn OFF (grey). While it is off, sending a file and/or message in the channel will not trigger email notifications to contacts in the channel.