While hotmail and Yahoo mail have "traditional" anti-virus scans for attachments, it's a disappoint to find that Gmail blocks attachments by extension!

I simply cannot understand how can the genius minds at Google consider this an effective "solution": genuinely good behaving executables are blocked simply because they are honestly named, while rogue agents can pass the inspection by simply changing their file extensions!

References:

• Gmail Help - Zipped Attachments
  
• Trick Gmail Antivirus Scanner: Send Any File Type with Gmail. (.exe, .dll, .com, .bat)