Archived email missing (2 years worth)

At the end of 2019 I archived all my mail. Recently I discovered the Archive Inbox folder is missing messages from April 2017 to March 2019.

I ran DbRepair.exe, to no avail. What happened to all those messages? Can I retrieve them?

ha!

When I first started out with eM Client, and transferred hundreds of emails, including content of other email Archive files, I lost the eM Client Archive, Its Folder and all content.

Multiple attempts to recover the Archive Folder, and/or its content were never successful.

As best I could I had to re-create the lost data.  Very, very time consuming.

In re-creating the data, I set up an archive Folder, which served the same purpose, but had an entirely new name, other than Archive.

The new functioning “archive” folder has retained all its data now for several years.

How do you “re-create the lost data” when the lost data consists of hundreds of mail messages which, by definition, you don’t have any longer?

My mail_data.dat file is 500MB. Those missing messages ought to be there. But I can’t open that .dat file. Does someone know how to do that?