I didn't expect to see an answer to this report after almost three years...
There is no gconf on Ubuntu MATE, because the desktop environment is not gnome.
Since I'm here, I want to report that the bug still exists on Ubuntu MATE 17.10 and on a couple versions between this and 15.04. I found a way to put a patch on the problem, but it's not particularly elegant. I entered a random email with a random password, so that Mail Notification can't connect to this email and always shows an error message. This way the icon is always visible in the tray even when there is no new mail.
I didn't expect to see an answer to this report after almost three years...
There is no gconf on Ubuntu MATE, because the desktop environment is not gnome.
Since I'm here, I want to report that the bug still exists on Ubuntu MATE 17.10 and on a couple versions between this and 15.04. I found a way to put a patch on the problem, but it's not particularly elegant. I entered a random email with a random password, so that Mail Notification can't connect to this email and always shows an error message. This way the icon is always visible in the tray even when there is no new mail.