These factors limit the ability to attach files to e-mail messages. location of sender recipient's ability to open file size of file type of operating system used

The answer is;

Recipient's ability to open file

Size of file

Sometimes, it might occur that the email message attachment you’ve sent to someone has an error or is corrupt in some way and thus, limits the recipient ability to open the file. Another factor is the size of the file. All email servers limit the size of the file attached in an email that a recipient can receive mainly because of security reasons. Google Mail, for instance, only allows you to send 25 Mbs only. This might limit the ability to attach files to e-mail messages as well.