Recently I have been testing a return receipt email utility called YesWare, which integrates with Gmail. When installed, YesWare adds a small toolbar to the top of your Gmail inbox and a small toolbar to the bottom of any outgoing mail you may compose. The outgoing email compose bar gives you the option of checking a box to track your email open status.
When you send an email with tracking enabled, you get a popup notification that your email was opened. This information can also be found in a dropdown (“events”) in the inbox toolbar.
I find this utility useful when I email clients or prospects – at a minimum you can tell how quickly a recipient will respond to you and you can identify prospects who may not use email much or cases where your email got sent to a spam folder.
Currently YesWare offers a free plan where you get 100 tracking events per month. $10 per month gets you unlimited tracking and some additional features, and $20 per month adds mail merge features and delayed sending.