Smartermail 5.x provides facility to enable or disable Greylisting for particular email account. Greylisting is used to block incoming spam mails. To enable or disable Greylisting option, you will need to follow the below steps:
 Login to your Smartermail web mail account.
 Click on Setting icon and go to "Accounts Setting".
 In Account Setting, go to "User" tab. Uncheck the check box "Disable Greylisting
" to enable Greylisting and check that box if you want to disable Greylisting
for your account.
 Click on "Save" button on the top and save your settings.
If you cannot see the check box "Disable Greylisting" then it may possible that your host has disabled the option "Enable Users to Override Greylisting
" from admin panel.
To enable or disable Greylisting for entire domain, kindly follow this steps