Emails and folders disappeared

[#1]

I have Plusnet and use Mail on Mac.  All my email folders have disappeared from my iMac and iPhone (not sure when this happened) and just have inbox, sent, deleted and drafts.  The folders have also disappeared from Webmail.  Any ideas about what has happened and how to restore them?

[#2]

Hi JonL

Check the thread @  'Lost folders and emails fter migration to Greenby'. Other people, including me, have lost emails and contacts. There are a few useful suggestions you can try but if you cannot find a backup, you may well have the same serious problem that I have. Greenby gets 95% one star ratings on Trustpilot. 

Chris