@dbuggmbh can you specify this “on some mails”? Maybe it’s not the deskapp but the mail or some of its attachements?
Although webapp and deskapp are basically the same, there seem to be some slight differences.
DeskApp primarily depends on the version of WebApp installed on the server. Using a modern WebApp could work, but is not actively tested (there may be features in the newer WebApp that don’t work with Zarafa like scheduling out of office for a time in the future).
@robing It would be great if the DeskApp is made available as a Universal App so that it runs natively (and without Rosetta 2) on the new hardware with the Apple M1 SoC. Also, the adaptation of the app logo to the look & feel of macOS Big Sur would be great.
If the file format is something your computer should be able to open, but it’s not opening correctly, its file format may be associated with the wrong program. … Instead of trying to open the attachment directly from your e-mail client, save the attachment to your computer (e.g., save it to your desktop).
In the end its security features of Mailstore that are interfering here (and usually for the right reasons). Mailstore seemingly sets a “content security policy” (csp for short) that prevents that it gets embedded from other domains (like you have webapp at https://kopano.domain.com/webapp and mailstore at https://mailstore.domain.com, using a different port for both also makes it a different domain for the browser).
DeskApp is configured to ignore this by default, that is also why there is a WhatsApp plugin only for DeskApp and not for WebApp itself.
What are your options? You could modify the webserver serving Mailstore to override the csp to allow embedding from your WebApp domain. We have been doing something similar when it came to the integration of Mattermost into Kopano WebApp.