

In some cases the Internet service (or the e-mail) provider may scan the incoming e-mails for malicious code and then remove all attachments that considered suspicious or unsafe. Contact your Internet Service and Mail provider. Open Mail app > bottom left, click the gear icon (settings) > right side, click Reading > under External Content heading, see if your email account is listed > make sure "Automatically download. If you see an "Opening " dialog asking if you want to save the file or open it with a specified application, that normally means that your Mozilla application cannot handle the MIME type internally, no plugin is installed and enabled that can handle it and you have not previously.

When you click a link to download a file, the MIME type determines what action is taken.
