Why POP3 in classic App Outlook 2019 HB and the Mail backup in the Outlook Web work...

Many thanks for your quick response, Diane!
<br />I shall switch to English, to be as clear as possibe in my further questions.
<br />Your explanations clarifys a lot.
<br />I have added my main mail account (IMAP) to the web app, and I can see those emails.
<br />I have added an outlook.com account to Outlook desktop, and moved calendar and contacts to that account.
<br />This works as well. Appointments and contacts are visible in the web app, and Android sync still seems to work.
<br />I might try to add outlook.com to Outlook on Android as well to see how that goes.
<br />Anyway, there are still a couple of questions left:
<br />

• I had problems adding an outlook.com account, using the cryptic one that is displayed in the web app.
  I then created a new one under my name, used that along with my Microsoft login password, and surprisingly this worked.
  <br />The cryptic one is still displayed in the web app - *** Die E-Mail-Adresse wurde aus Datenschutzgründen entfernt. ***, can I change this?
  
  <br />
• Now, when I start Outlook Desktop, it always goes to the Inbox of the outlook.com account.
  How can I change this so it's the inbox of the IMAP mail account? (as I'm used to)
  
  <br />
• I assume the mails in the outlook.com account are just a copy of the associated mail account.
  I.e. I cannot do all mail work from @outlook.com but still need to visit my IMAP account to delete mails. Correct?
  
  <br />
• For Outlook desktop, is Microsoft's recommendation to just use the outlook.com account, or to also have the associated accounts included?
  
  <br />

Many thanks for your advice.
<br />Karsten
<br />

Hi Skypper G.,

thanks a lot for your responce!

The policy is published more than 7 days and that's the problem that I see only the "Use parent folder policy" option in Outlook Web App. As I understand that means that I still don't have any policies
within Outlook. In Compliance Center the policy is active (Success Status).

Do you have any other suggestions why is this connection problem?

Thanks in Advance.

Thanks.
<br />May I ask again for sending the answers in English.
<br />Is there a synchronization program which works for google and IMAP e-mail accounts?
<br />Before the trouble regarding e-mails I had 3 calendars in outlook now it is only one.
<br />Are the manual saved PST and by the windows backup tool saved file useless?
<br />Where are calendar and contacts located in Outlook?
<br />Can I access the OST file, how? There is one OST file for each mail account.
<br />
<br />Kind regards
<br />Erwin
<br />

i think i found the problem. easeUS Backup Software. i really forgot that i use this. i tested it. every time i do the "system backup" job it deletes the .ost files. i dont know why. i did SFC /scannow and "dism" to my system. rebootet. deleted the backup
job & created a new one. but the issue stays.

so i will check with their support if this is a known issue.

glad that file history and synology backup are not a problem.

And the login with the Android outlook.com app did work with the outlook.com address.
It's a shame that about 10 trys to sort this issue with MS support did not work. When the actual solution is that simple. Also it's a shame this is not mentioned anywhere, that it has to be an outlook account.