After upgrade: what's this envelope systray icon, and how do I get rid of it?

I've just upgraded from 13.04 to 13.10 and everything seems to be running fine. I have a couple new icons in my systray, though, and one of them -- the envelope icon -- is a mystery to me:

enter image description here

It looks like a chat notifier (clicking it gives "Available", "Away", "Busy", etc., indicators) but I don't use Pidgin (never have), or it could be an email indicator but I don't use Thunderbird (never have). There's nothing else I can see (left- or right-clicking) that identifies it.

I'd like to get rid of it, but "Startup applications" only lists the ones I have optionally added, and this is not among them.

Any help appreciated!


I just remove it a few days ago by running the following command in terminal:

sudo apt-get remove indicator-messages -y

A re-login is necesary.


To remove the Mail icon, open the Terminal, and copy & paste the command:

sudo apt-get autoremove indicator-messages

Now press Enter and enter your password, then press Enter once again

Now you need to restart lightdm with the following command in the Terminal

sudo restart lightdm

Press Enter and enter your password then press Enter, lightdm will flash and the Mail icon will no longer show.

Credit to scouser73 from this question