Changing the “email-provider” means changing my job 
– it’s my employer and I am working in public/health sector with patient-data – so Google & Co. wouldn’t be good alternatives 
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But I see that using another strategy for managing my emails (such as archive folders per year or so) may alleviate the problem. I will try whether I can get a good workflow with eM Client. In any case, I just wanted to describe the situation. Thanks for listening and taking my use case serious, Gary!