Send email from Another Address Using Gmail Sans On Behalf of

If you have ever used Gmail to send messages with one of your other email addresses listed in place of your Gmail address, you must have noticed that Gmail adds a custom From to it. Well, since the e-mail are sent by Gmail’s server but from a non-Gmail address, it displays the original Gmail username in the Sender field indicating that it was send On Behalf Of your other account. This is in compliance with the mail’s delivery protocol that helps in preventing the mail from being marked as spam.

Majority of e-mail programs just show the From address and not the Sender field. However, Gmail shows these messages as coming From username@gmail.com On Behalf Of customaddress@mydomain.com, which is quite an upsetting experience. Finally, Google-mail has decided to drop the On Behalf Of and allow the users to send messages from third party SMTP servers.
This piece might appear a bit ambiguous to most of you. Let me explain, surely you might like to use Gmail’s web interface for managing e-mails of other accounts. But, this might not be possible if you don’t have Google Apps on the mail server, like for your work account.  For this you require a simple workaround - just auto-forward all the incoming messages on your work e-mail account to your Gmail account. This will also allow you to send messages and make them appear as if they were sent from your work account and not Gmail account. Until now Google included a On Behalf Of your address with the message, while displaying the name of the your Gmail account from which you sent the message.

Now, instead of using Gmail’s servers to send the message, it would use the servers where your other email address lives.
If your other email provider supports POP and/or IMAP access, you message would be send via the other accounts outbound server to your recipients inbox.

In order to use this new method follow the steps below

Step 1: Go to the Accounts page under Settings, look for the Send mail as option and hit the edit info

Step 2: Choose the option Use your other email provider’s SMTP servers

If your other email provider doesn’t support authenticated SMTP, or restricts access to specific IP ranges, Gmail retains the original method as well.

Although this is might not be used by most of the people, still all credits to Gmail for working out a viable solution to get rid of the On Behalf Of.

Source: Gmail blog