Two mail boxes full of emails disappeared

Hi,
I keep 13 mail boxes (none smart) on the bar beside my incoming emails as well as the basic ones such as "Sent" They are "on my Mac". not in the Cloud. Recently they've disappeared and two called Rocovered Messages have appeared, which are empty. I've been into Time Machine, but all I can find are all the emails which came in on particular dates.
This is a MacOS Sierra(Retina SK 27-inch, Late 2014)
Please can anyone help?

greentick

Are the emails from one email provider, or are there multiple accounts that are affected?

Two mail boxes of emails disappeared

ferrarr said:

Are the emails from one email provider, or are there multiple accounts that are affected?

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They are from numerous different people. thank you

That was not the question. What Bob asked was whether or not these were multiple accounts FOR YOU, not who they came from. So, are they from one account, or more?

MacInWin said:

That was not the question. What Bob asked was whether or not these were multiple accounts FOR YOU, not who they came from. So, are they from one account, or more?

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Sorry, they all came from my account.

To restore from Time Machine for Mail, you first open Mail, then with Mail open, click on the Time Machine icon on the Dock. From there you should be able to go back to find where the last version of the missing mailboxes were to restore them.