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. Full article (421 words) »