Hi Alex, indeed you can - this functionality has just been added to the latest beta builds of SpamFilter:

// New to VersionNumber = '3.5.4.701';
{TODO -cNew : Replaced the option "BlockBlankEmailsWithPDFAttachments" added to build 3.5.4.700 with the more generic "BlockBlankEmailsWithAttachments". This allows admins to block blank emails containing any one of a list of unwanted attachments}

See this post for more information on how the setting is used within SpamFilter.ini.

If you are a licensed user, you have access to the latest betas with the new feature.  If you are evaluating, the feature will be added in the next official release.

Stephen

EDIT: I realized that I need to clarify... this setting does not include a file size range like you had suggested.  Also, I do not know whether or not you can override the default blocking action (null vs. quarantine).


Edited by sgeorge