You can get rid the "via" part. Here's the details:

1) SPF and DKIM

Firstly, you would need to set an SPF record for the domain you are sending emails from and enable DKIM as well. These are primarily for identifying your messages against spam.

2) "From: anything@yourdomain.com"

Secondly, make sure you are setting the “From: ” header to be an email address on the domain you are sending messages from. Don’t pretend to be someone else. Use “From: someone@abc.com” if you are sending the messages from abc.com, rather than anything else, such as blah@def.com, or yours@gmail.com, or whatever. If you want the recipient to reply to your Gmail email instead of your domain email, use the “Reply-To: ” header. “From: ” must always be the domain email that you are sending the email from.

3) "Return-Path: return@yourdomain.com"

Thirdly and most importantly, set the “Return-Path: ” header to be the same domain as that of the “From: ” header. Use the 5th parameter of the mail() function for this:

mail('recipient@example.com', 'Subject', "Message Body", $headers, '-freturn@yourdomain.com')

So the Return-Path of this message would be “return@yourdomain.com” (the email address immediately following the -f switch). The $headers parameter should contain all the necessary message headers. Make sure “From: ” is something@yourdomain.com.

After these steps and measures, Gmail should now completely trust your messages from yourdomain.com. The ‘via‘ field of your messages should be gone and the ‘mailed-by‘ field as well as the ‘signed-by‘ field should be correctly showing up as yourdomain.com.

Hope it helps!