Package evolution-ews can't be installed from buster-backports

[pirx67@gmx.de]

Hi,

I need to use the package evolution-ews to connect to an exchange server
in the web to access my emails.

Unfortunately the package evolution-ews is not included in the Debian Buster
stock distribution. It is only available on buster-backports even it was
available in stretch and jessie in the main distribution.

So I added the file /etc/apt/sources.list.d/buster-backports.list with that line
deb http://deb.debian.org/debian buster-backports main

I updated the package lists and tried to install the evolution-ews package but
apt-get won't install it:

root@host:~# apt-get install evolution-ews
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 evolution-ews : Depends: libedataserver-1.2-23 (>= 3.30.5-1.1~) but 3.30.5-1+deb10u1 is to be installed
E: Unable to correct problems, you have held broken packages.

I don't get why evolution-ews (3.30.5-1.1~bpo10+1) is linked against
libedataserver-1.2-23 (>= 3.30.5-1.1~) even if the rest of evolution(-data-server)
is happy with still 3.30.5-1+deb10u1.

root@host:~# dpkg -l  libedataserver-1.2-23 evolution evolution-data-server
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                        Version          Architecture Description
+++-===========================-================-============-==============================================
ii  evolution                   3.30.5-1.1       amd64        groupware suite with mail client and organizer
ii  evolution-data-server       3.30.5-1+deb10u1 amd64        evolution database backend server
ii  libedataserver-1.2-23:amd64 3.30.5-1+deb10u1 amd64        Utility library for evolution data servers

Notice that the evolution-data-server package itself is of version 3.30.5-1 (+..) and not 3.30.5-1.1
like the evolution core package.

Any hints to resolve this? Who is doing that backport that I may contact?

Trying to install with synaptic is looking somewhat more weird. When I mark
evolution-ews for the first time in synaptic then I get this message:

evolution-ews:
  Depends: libedataserver-1.2-23 (>=3.30.5-1.1~) but 3.30.5-1+deb10u1 is to be installed
 Depends: libmspack0 but it is not going to be installed

When I after that mark evolution-ews for the second time for installation then
synaptic seems to consider libedataserver-1.2-23 from buster-backports and so
pulling in libedataserver-1.2-23 with version 3.30.5-1.1~bpo10+1.

But that new version is incompatible with a lot of the Gnome stuff which is then
automatically marked for deinstallation in fact breaking the system. Some
examples of important packages marked for deinstallation are:
gdm3, gnome, gnome-core, gnome-shell, gnome-calendar, ...

What can I do now. Except asking the package maintainer of the evolution-ews
package in buster-backports to build the package differently.

Best regards,
    Stefan