Forward email without keeping a copy?

Hi there,
I'm new to cPanel, have been using Plesk for years.
What I'm trying to do is this.
Forward all mail to address a: someone@domain.com to another address: someoneelse@domain.net
domain.com is hosted by me, but what I'm trying to do is avoid any msg's sent to someone@domain.com ending up sitting in that mailbox on the server.
I have been doing some reading, & it *may* be that I don't actually need a mailbox for the forwarder to work - is that correct?
This is how I had things set up on my old hosting under Plesk - no mailbox, just a forwarder.
What exactly is the difference between a forwarder & an alias in this situation (under cPanel)?
Is one a better solution than the other?
Any advice very much appreciated.
Thanks,.
Jason

 

I should add, are there any tools or services I can use to help troubleshoot email issues?

 

Thanks, am waiting on the hosting company to come back to me now as I'm still having no luck getting the forwarded email.

 

Ok, I'm still not having any luck.
So...

1. should I use a filter or a forwarder?
2. if a filter - should it be an account level filter, or a user level filter? (I have multiple domains under this account).
3. if a filter - are there any recommended ways to set this up? (see attached)

Is it really this difficult to set up a mail forwarder in cPanel? Or am I just making a meal of it?
Thank you