If you want notifications when a new email is received at your isp email server without having to keep an email client running I use Poppeeper running in WINE.
It's a windows program but it works very well in ubuntu using wine. It can be setup to check several email accounts at any interval you like. You have to install a plugin in poppeeper to display a notification bubble if you want a visual notification or you can leave it as a standard install and poppeeper will display a blue flag in the system tray at the top of the screen when a new email is received, you can then double click on the icon and it will open a screen where you can preview the incoming emails / delete unwanted ones even before you open up your email client.
I wouldn't be without it.