I sometimes forward messages which I’ve received or a sent as attachments to someone else.

Instead of receiving the attachments that I sent them, they receive them as noname.eml attachments which they cannot open. When they click on it, they only see gibberish.

This doesn’t happen for everyone but mainly for people who are using Gmail, Outlook.com/Hotmail or another web mail account rather than using Outlook.

How can I make sure that they receive the email attachments as it should and that they can read it?