Proposal: (No?) email client for Ubuntu 17.10

[Jeremy Bicha]

In 2011, we switched Ubuntu's default email client from Evolution to
Thunderbird. Six years later, I think it's time to take another look.

Should we even install an email client by default? The question is not
whether it's useful, but whether it's useful enough to enough people
to justify it being installed for everyone.

- Ubuntu GNOME 16.10 included Evolution but 17.04 has no email client
installed at all. The decision disappointed a few people but there
hasn't been much negative feedback at all yet.

- GNOME Release Team member Michael Catanzaro recommends not
installing an email client by default since there isn't an app that is
both well-maintained and very well-integrated into the GNOME 3 style.
[1]

- It's believed that most people just use web mail now, often along
with apps on their smart phone.

- A problem is that those who do prefer to use an installed email
client do not all prefer the same one!

If we do include an email client, which one?

Thunderbird (TB)
-------------------------
1. TB is still built with GTK2.
2. TB is a community project now and Mozilla no longer pays developers
to work on it.
3. It looks like TB will have a lot of work to do next year once
Firefox drops traditional extension support with FF57. This work might
be shared with other apps that use Mozilla code.
4. TB does not integrate with GNOME Online Accounts.
5. TB has better Unity integration than Evolution.
6. There was a proposal a year and a half ago to turn TB into a web
app but I don't think that went anywhere. [2]

Evolution
--------------
1. The UI doesn't fully embrace GNOME3 app design style, but it is
closer than TB.
2. Small development team.
3. Evolution is not available on other operating systems.
4. Evolution is relatively easy to co-maintain with Debian.

[1] https://blogs.gnome.org/mcatanzaro/2016/09/21/gnome-3-22-core-apps/
[2] https://groups.google.com/forum/#!topic/tb-planning/h97q9cDUZOU

Thanks,
Jeremy Bicha