Spam Filter stops users who are not on your contact list from sending you a private message. This can help you stop receiving unwanted private messages.
To turn on Spam Filter in the iOS client first tap the Settings icon.
Select General under Settings and tap.
Then click spam filter on by moving the dot to the right.
Please ensure you re-log for the changes to take effect.
On the Home tab select the Settings icon or press the button settings/menu button on your Android device.
Ensure Spam Filter is checked.
Once checked, you will need to re-log for the changes to take effect.