I'm shocked this product doesn't have more reviews. Have to offset the one negative review with a positive.
I've been using Mailtrack for a year now. Prior to that I tested many different online tools to track email from Gmail and none worked well enough for. HubSpot's SideKick worked wonderfully, but then became more complex as they integrated it into their CRM.
For me, I want simplicity. I want to know when my emails were read. That way it saves me the guess work of the email being delivered and read.
I highly recommend using Mailtrack and purchasing the Pro version! It's worth the minimal cost.
Unobtrusive (if using Pro version). Easy setup and integration with Gmail. Android notifications on phone.
Could use a better integration with Gmail for Android. Currently uses labels to add check marks for read and unread.