Creating a Fillable PDF and adding a Hyperlink email with completed PDF attached

I design many Corporate forms that have to be fillable. I create a Link with a email and attach a completed PDF which autopopulates into an email with completed form attached. Some end users it works and some it do not, can someone explain why this is happening. 

When I creat it and then test it, it works perfectly but some others it will not work.

Would it be becasue they are not on the same Outlook Account, can gmail and others use this feature?

I need help!!

thanks

Darrin