Create a generic POP Email account on your host (with Cpanel for example), I will call this account ‘John’. Create a forward email address yourname-at-yourdomain.com, and point (forward) it to your Gmail account.
Go to the Settings page in Gmail, Accounts and Import, click Send mail from another address, and add your forward mail address you just created (yourname-at-yourdomain.com). Use the generic email address as credentials for authentication.
Now you can send emails as yourname-at-yourdomain.com without having the ‘On behalf of’ line in the From:-field.