The content filter has a condition to trip if a header doesn’t exist. However, there is no easy way to catch a header with no content at all.
This rule will trip on a blank subject header (where the header DOES exist, but has no content)
[Rule001]
RuleName=If subject is NOT empty, Skip next rule
Enable=Yes
ThisRuleCondition=All
ProcessQueue=LOCAL
Condition01=SUBJECT|reg exp|AND|^..+$|
Action01=skip rule|"1"
[Rule002]
RuleName=Subject IS empty!
Enable=Yes
ThisRuleCondition=All
ProcessQueue=LOCAL
Condition01=SUBJECT|exists|AND|
Action01=move to bad Msg|
UPDATE 2009/06/17: For some reason this rule was completely broken, both by WordPress inserting smartquotes, and a logic error. My apologies, it has been corrected and tested on MDaemon 10.0.5, it should now work as advertised.
Detecting a blank header in the content filter by Dave Warren (everything-mdaemon.com) is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
Got this from [md-cfilter] reject “no subject”
This works for messages with blank subjects
emails – outbound
RuleName=Blank
Enable=Yes
ThisRuleCondition=All
ProcessQueue=BOTH
Condition01=SUBJECT|reg exp|OR|^ *$|
Action01=move to bad Msg|
Noy,
This is true, if the subject header contains a space like this: “Subject: “, however if the subject has no trailing space (like “Subject:”) then the “^ *$” format fails to trip.