Upon receiving a new mail, Thunderbird notifies the user through a screen notification. The downside is, after the notification dissipates, there is no clue hinting a new mail is pending besides putting Thunderbird in front.
The idea here is to keep the user notified there is a new mail pending, by either:
I know there are external utilities such as Birdtray, but i find them unpractical due to required manual configuration of each inbox to monitor. Having the feature within Thunderbird should make it easier to manage.