Android Question Downloading .apk received as raw.bin

Hi all,
I just tried to share my apk application through e-mail to a friend of mine.
I used yahoo e-mail service. I attached the apk.
The user tried to download the apk from his tablet (Android 4.2.2) but in download area
it is shown as raw.bin
What am I doing wrong or what? I thought that this would be the easy part of developing
an application using B4A
Appreciate any help
regards,
mike