There was a question submitted today about the verification process at Gmail.

even though SPF authentication is passed, a via is added to mail sent from a webserver. The return-path is not the same as the visible from field, but there’s no way for me to change it. Does that mean I won’t be able to get rid of the via?

This actually ties in to some research Steve and I did a few months ago about how and when Gmail is displaying the “via” in their interface. We generated 90+ different emails with various From: addresses, Return-Path: addresses and passing and failing with both SPF and DKIM.
After crunching all the numbers down, I created a table with all the conditions.

As you can see, there were only a very few conditions that generated the “via” display in the Gmail interface. In cases where there was any domain match between the visible from: and the return path, either the exact domain or a subdomain, there was no “via” displayed, even if authentication failed.
But, when we look at the cases where the domain in the Return-Path is unrelated to the visibly displayed From, then we start to see the cases where Gmail displays the “via.”

So the answer to your question is as long as the webserver is a different domain than the visible From: address Gmail will display a via. You may be able to have no via if you provide no authentication, but Gmail does what it calls “best guess” SPF so even that may not work for you.
 

Authentication • gmail • via