Can we enforce Windows 10 app to retain all old emails (not archiving them)?

Question

I migrated to the native email app in Windows 10 in order to reach emails from my new employers server/exchange. The account is of Outlook type.

It was convenient to set up and I used it for a few months now. After coming back from Christmas and New Year holidays, I found out, however, that all my folders into which I did painstakingly sort my old mails (all mails relevant to particular project to particular folder) are empty now, (emails in them, it seem to have crossed some internal threshold of age are removed from being available) and they force me to search for my older mails "online"... the truth is I do not even know what to search for. What was all the conversation relevant to the projects etc. I just want my old mails being in folders where I did put them.

Is there any way to enforce that?

The way it works seem to be somewhat different form email archiving, yet somewhat similar to it. ... but without archiving it into any available archive on the hard drive (and with lost structure)

I couldn't google out any relevant answer or rule. Mail app in Windows 10 seem rather simplistic in it's settings and option, even primitive. It seem impossible to change parameters relating to the duration of time emails are kept available (without the function "search").