SOLVED! "Outlook blocked access to the following potentially unsafe attachments" message in Outlook

Just handled a troubleshooting... when sending an email with an email as attachment, the one received the email cannot find the attachment. Instead, Outlooks showed a message...

"Outlook blocked access to the following potentially unsafe attachments"

Google....most people recommend to create a registry key to Outlook to avoid blocking of certain file extensions, which will work in most cases:

https://support.microsoft.com/en-us/help/829982/-outlook-blocked-access-to-the-following-potentially-unsafe-attachments-message-in-outlook

Sadly, in my case, it didn't work. 

SOLUTION:

Finally, the fix that works for me... the attached email has a NAME TOO LONG, I need to change the name to a SHORTER name before sending. That's the fix in my case!

By default Outlook uses the "Subject" of the message as the filename of the attached email. So, change the "Subject" to a shorter one.

This simple fix does not even need a registry edit or install a software!