[Nexus 6 Themes and Apps] garyd9:
On the nexus6, google dropped their AOSP "Email" app, and replaced it with a more function GMail app. The new gmail app was given the ability to sync MS Exchange accounts (as well as pop, imap, etc.)

However, I personally don't like using gmail for my email. There are a couple of reasons, but the biggest one is that gmail doesn't allow a "combined" inbox view. (I sync with multiple MS Exchange servers, and I really like being able to look at a single list instead of having to tap all around to check individual accounts.)

So, I recompiled AOSP (for lollipop, of course) and pulled out the email (and exchange server service) apps, copied them to my device, and everything works the way I want again.

I'm sharing this non-work with other XDA users with the following caveats:

1. This is google's work, not mine. I've just recompiled it. The source is completely unaltered from AOSP 5.0.0.r5.

2. I'm not going to support this. I'll give detailed instructions on how to copy the files to your nexus device, and I might even package them into a recovery installable .zip file (if I remember tomorrow and have free time), but that's it.

3. If you understand and accept everything that might go wrong in doing this, then great. If you don't, please ignore this post and read another one.

That being said...

You need to have a rooted device, and be fluent with adb and a shell. If you aren't, just wait until I (or someone else) packages this into a zip you can install in recovery.

Really quickly, then:

adb push Email.apk /sdcard/
adb push Exchange2.apk /sdcard/
adb shell
su
mount -o remount,rw /system
cd /system/app
mkdir Email
chmod 755 Email
cp /sdcard/Email.apk Email
chmod 644 Email/Email.apk
mkdir Exchange2
chmod 755 Exchange2
cp /sdcard/Exchange2.apk Exchange2
chmod 644 Exchange2/
reboot

After that, you'll now have two "email" apps in your app drawer. One is a shortcut to gmail, and the other is the one you just copied in. (I think the gmail shortcut one is located in "/system/app/PrebuiltEmailGoogle" in case you want to get rid of it -- or read on for another way to get rid of it) Figure out which one is which, and you'll be good to go!

Yes, the AOSP email and gmail stuff can co-exist. Even the exchange services can co-exist.

However, the second "email" app icon is annoying. Instead of deleting the apk from /system, you can just go into settings->apps->all, and find the "Email" app that's 6.7MB (or the smaller of the two) and disable it.

If you want to disable the gmail version of MS Exchange support, go into settings->apps->all and notice that there are two "Exchange Services" apps. One of them is "version 6.xxx" (which is the one for gmail), and the other is "version 5.0.50.50.50.-eng-garyd9.xxxx". So, you'll disable the one for gmail and leave the one with "garyd9" in the version tag enabled.

Note: Nova Launcher's "teslaUnread" plugin will not work with this email.apk as a native google email app. The reason is simply because this isn't "com.google.android.email". It's "com.android.email". (It's different...)

Edit: For a recovery installable .zip file: scroll down (or just click here: http://xdaforums.com/showpost.php?p=57161503&postcount=6)

Another Edit: Be warned that there are some problems with this. If you have multiple email accounts and used the "combined view", it can crash when you try to view an email. As well, under some circumstances, it will stop picking up mail (and contacts, etc) all together (unless it's manually polled.) I'll get around to looking at these issues at a later time.

Take care

Gary

UPDATE (2014-12-12): updated the email.apk with one that doesn't crash when viewing the "combined" view. Exchange2.apk still doesn't do push email properly, but that's going to take a bit more time.