After more than 6 months problems and a lot of support with no help I found out that the "email client protection" caused the problem:
Very - very - slow or no syncronisation of my IMAP emails via outlook 365
Affected was mainly only one provider - web.de
US live.de and other german provider emails worked better but also not perfect as years ago
I bought a new PC, clean installed Windows 10 and office - nothing helps
after switching off the protection it was immediately solved!
I don't know if the provoder web.de was the cause ore eset - but doesn't matter - I'm really angry
