how can i retreive the previous mail in my mailboxes?

Carene, not sure what you’re asking.  If you have just stated using Em Client and your email is using the IMAP protocol, all your email will be pulled into EmClient inbox, sent, junk, …  If you’re using POP3 (this will test my memory) I believe you will only get the messages that have not been downloaded/received before (new message).  Hence I recommend IMAP when possible.
Let me know if I’ve missed the question.

As a follow-up to Artie’s accurate response, maybe you didn’t import messages from your old email client? You can go to menu/file/import and select the appropriate application/files.

Thank you both for the replies Artie and Jay. I had been using eM Client (with access to all the previous content ) on a trial basis. I chose to go for the free licence and on activating it , all previous content in the folders disappeared. Whats the IMAP protocol Artie? where should i be looking for it?

a tiny amount of legwork and i found imap!