^ Instead of an add-on you might consider looking into
Pop Peeper (Note: If all you want is a "Notifier" for email then the free version is all you need and you can ignore all my comments regarding available add-on options). You are not only notified of new mail (with many options on how you want to both "Check" mail and be notified but you can also read all email messages (and send if you like) using Pop Peeper (automatically logs into any email account you access when reading incoming messages). And you not only have a list of all email accounts but all messages are displayed for each account which can be listed either individually or as a group.
Take a look at
POP Peeper: Email Notification --- Pop Peeper provides the largest array of support for Email Providers that I'm aware of. The free version provides voice notification when new mail arrives (you can have it say whatever you want which would apply to all incoming messages). The add-on "Voice Notification" process that the optional "PlusPack" plugin provides is really great however and a big reason why I use Pop peeper because it provides additional information regarding incoming email as the messages arrive (current price for "PlusPack" is only $10.00 and for me well worth it). With the "PlusPack" I am able to hear whatever I want to hear about the messages at the time the message arrives (which I haven't seen in any other Email Client so far). I've got it setup to say "You've got mail" and then I hear listed off the sender and the message subject for each message received at the time (besides the alert there is mail, you can have account name, subject, sender or any combination of these three as part of the voice message). Being able to hear more than just the typical "You've got mail" (as I mention before, you can have it say whatever you want of course) is a very helpful added convenience because also knowing WHAT email has arrived (who the sender is and/or what the subject is) for me is well worth the $10.00 it costs for the "PlusPack" not to mention some other added features this option provides as well. Most of my messages are not important enough to have to deal with on the spot, by getting besides just the typical voice notification that email has arrived but also getting who's the "sender" (or optionally the email "subject") then I always know when an important email has arrived that I need to deal with immediately.
If you were to use Pop Peeper as more than just a "notifier" that is to send messages then the biggest issue for me was that with the FREE version of Pop Peeper there is no Spell Checker. What I did was install TinySpell which is a very low resource spell checker that can be assigned or de-assigned to any app you choose so that way I can have a Spell Checker without having to buy the more expensive
Pop Peeper Pro (link explains the added features). I did that for a while but eventually went with the Pro version because there's quite a bit of extra security that comes with Pro, but that's totally optional and you get updates for life either way you decide, either FREE or Pro.
Note: I have inside info that the Pop Peeper PlusPack will be going up in price from $10.00 to something in the range of $12.95-$14.95 in probably a matter of weeks so I thought I'd give you a "heads up" on this. The Pro version is of course totally optional and as I mentioned all updates for what you do have are for life, so it's something to consider that would bring added value for only $10.00 current price. The
PlusPack also has RSS protocol and a Backup and Restore utility among other things as well.
I personally use Pop Peeper as my primary method of monitoring Email messages. The Interface is straight forward and easy to work with and is not only very robust but can handle all of my Email Clients of which include Web Mail accounts such as Outlook, Yahoo, Gmail, Mail.com, Excite, Juno as well as Internet Clients such as VFEmail and Fastmail (Pop Peeper will seamlessly handle virtually all of them that I'm aware of).
