how to filter blank subject mail by using Transport Rule
1. Click on Transport Rules tab, click button New Transport Rule.
2. Type in the name of the rule, such as "Blank Subject Filter".
3. In the Step 1. Select Condition(s) box, select the when the Subject field
contains text patterns condition. If you want to filter emails with blank subject
or blank body, choose When the Subject field or the body of the message contains
text patterns instead.
4. In the Step 2. Edit the rule description (click an underlined value) box, click
the text patterns blue underlined words. In a pop-up new window, type ^$ and then
click Add. Click OK to close the window and then click Next.
5. In the Step 1. Select Action(s) box, select all the actions that you want to be
applied to this rule.
6. Modify the settings if you want to set Exceptions to this rule in the Exceptions
window. When finished, click OK and click Next. You may choose to exclude internal
emails from this rule.
7. Review the Configuration Summary. If the configuration of the new rule is
correctly set, click New, and then click Finish
