Why does testing a forwarder sometimes not work?

Please don’t test a forwarder by sending an email to it from the email account that you are forwarding to.

For example:

If you forward email from one@mydomain.com to one@gmail.com, and you test this forwarder by sending an email to one@mydomain.com from one@gmail.com, this will not appear in your inbox at one@gmail.comm as expected and you may think your forwarder does not work.

This is because some email providers like Google Gmail don’t allow such messages (‘To’ and ‘From’ is the same email address) to appear like any normal email, because you already have a copy of it in your Sent folder.

Always test forwarders from a different email account that isn’t involved in the forwarding.