Why Gmail user can't see my forwarded email?

Please be noted that when an email is forwarded out it will be saved as a .eml file, and .eml file is not supported by Gmail.

To avoid this problem you can select “Text” before you click on “Forward” when you want to forward the email out. Once you select “Text”, the forwarded message will not be sent out as .eml file.

Alternatively, you can also click on “Edit” to edit the email before sending out.