Thanks for a bug report, but the 3.10.4 is way too old. If you want any support of that ancient version, then ask Ubuntu. I do not know what Ubuntu 15.04 ships, I cannot help there. Just note that the current stable version is 3.16.3 of both evolution and evolution-ews.

The screenshot shows multiple issues, on both top and bottom parts. The upper has probably some missing folders, while the later has missing icons, which might be due to missing (not installed) icon theme.

I am not aware of any evolution-ews option to hide certain folders from the view, thus I guess your local cache got out of sync probably. I would try to get rid of
   ~/.cache/evolution/mail/<ews-account-uid>/
folder, with evolution being closed, then run it and let it download the account information from scratch.

In any case, 3.10.4 is out of question, as I said, 3.16.3 is the current stable version.

Now running under Ubuntu 15.04 in VirtualBox. Default evolution is still an
old version, 3.12.11. Following
http://linuxpitstop.com/how-to-upgrade-evolution-email-client-to-3-16-on-ubuntu-15-04/
"How to upgrade Evolution Email Client to 3.16 on Ubuntu 15.04" I installed
evolution 3.16.0 (Debian package only). The problem persists, with "Inbox"
set to a single very old message. "Sent items" is correct and completely
up-to-date.  "Deleted items" is correct and up-to-date. Web access using Firefox etc shows correct Inbox. I haven't managed to build 3.16.3 from source yet.

(In reply to Milan Crha from comment #1)
> I am not aware of any evolution-ews option to hide certain folders from the
> view, thus I guess your local cache got out of sync probably. I would try to
> get rid of
>    ~/.cache/evolution/mail/<ews-account-uid>/
> folder, with evolution being closed, then run it and let it download the
> account information from scratch.

Did you try the above, please?

Yes I did try that on the upgraded system, no effect. I have also installed evolution on completely new VirtualBox VMs with no previous installation and created the ews account from scratch. That's both 3.12.11 from Ubuntu 15.04 and 3.16.0 from linuxpitstop. I just cleared the cache again on 3.16.0, no effect.

Is there anything else I can try, please? This is a real blocker as I can only read my work emails using a browser not evolution any more. I can still send new mail, see the Sent mail and Deleted mail folders okay from evolution, but I can't see the Inbox properly

The only option I can think of is to cleanup the cache again, then run evolution with EWS debugging on and see what the server returns. The cache cleanup is shown above, the the logging is turned like this:
   $ EWS_DEBUG=2 evolution &>log.txt

Please note that the log.txt will contain raw communication between the server and evolution, which includes your folder names, server addresses, and if you happen to download any message then also message contents. Thus if you consider all this information private (I do), then feel free to send the log only to me, with a reference to this bug report in the subject, thus I'd not overlook it in my spam folder. If you include also screenshot of what folders are seen after the initial folder fetch in the Evolution, then it'll help. I guess it'll be the same as the image in comment #0, but just in case.

Thanks Milan, log file sent as requested. But now for some bizarre info: from a backup, I installed an old version of the cache files, from before the problems started. Just the cache files. And it started working again, showing the Inbox at the top of the list and with the right contents. That was for Ubuntu 14.04 with Evolution 3.10.4. So I tried using this old cache and old configuration for Evolution 3.16.0 and that worked too (for a little while)! So a clean cache fails while an old cache works.

In the meantime I am back to a working mailer so my desperation is reduced :-). But I would still like to know what is going wrong, of course!

Thanks. Looking into the log there are reported all the folders, and I didn't notice any related runtime warning there. The only semi-interesting thing is that there are shown two "Inbox" folders. One it the main Inbox, the other one is under "Journal" folder. This might not confuse evolution-ews in any way, because the parents are stored properly, but I can be wrong, because the log shows that the Journal/Inbox folder is being updated (checked for items) too.

I would try to login to the OWA (Outlook Web interface) on the server and delete/rename the Journal/Inbox folder to something else. According to the log it contains one message. Your real Inbox contains 341 messages.

Great! That fixed it. I renamed the Journal/Inbox folder and now I can see both properly. But the renamed folder (JInbox) is showing as a toplevel folder, with no Journal folder in Evolution. So it appears that with an empty cache it looks like two toplevel Inbox's and the second hides the first. With the old cache, Journal/Inbox as well as Inbox shows. With OWA and M/S Outlook neither the Journal folder nor its subfolder appear - some sort of special case?

Thanks Milan

It wasn't that simple, after all. I created a Journal subfolder Inbox, but it had set journal type, thus it didn't affect UI in the Evolution, but when I moved there a mail folder, then it broke things as for you.

I made a change to simply ignore any mail folders out of the mail hierarchy of the user (except of subscribed public or foreign folders), which fixes the possible clash in the folder names.

Created commit fa32c63 in ews master (3.17.90+)
Created commit 8f2700c in ews gnome-3-16 (3.16.5+)

Thanks Milan, your work is very much appreciated. It's one of the things that keeps me sane, as the only person running Linux in a Windows shop!