Please don’t test a Gmail forwarder by sending an email to yourself from the Gmail account that you are forwarding to. For example:
If I forward email from firstname.lastname@example.org to email@example.com, and I test this forwarder by sending an email to firstname.lastname@example.org from email@example.com, this will not appear in my inbox at firstname.lastname@example.org. Google conversation view doesn’t allow this to appear like any normal email, because you already have a copy of it in your Sent folder. Test the forwarder from a different email account that isn’t the one you are forwarding to.