Gmail allows sending mail from your own SMTP server
I use my Gmail account to send and receive from all of my other email accounts (bradsimpson.com, swashbucklerinteractive.com). Previously, it would display (in email apps like Outlook) that the email was sent "on behalf of" my Gmail account. Now, you can change your account settings to send mail from your domain's outgoing mail server. Nice one, Gmail.
Gmail Blog:
Send mail from another address without "on behalf of."