Outlook sent Items delete - post serving notice period

After serving the notice period of 45 days, I left the company. On the last day, the Hr. did not completed my Off boarding ( off boarding procedure was provided by the off shore client already). I was working for a LLP firm which had a contact with US clients. On the 46th day, I received 7-9 calls and several OTP's to log in to the email which was provided to me by the clients end, also one employee asked me to assist him with a query. So, I "opened the Outlook and firstly replied on an email - to redirect a clients issue to the correct POC as I left the company". My mailbox pop up with - Mailbox reached maximum size, so in order to work, I deleted the sent items which created the space in outlook. Within 30 days in rushed back to my employer (by taking an appointment) to recover those sent items emails from delete items- but my employer refused to show me the inbox!! The next day, my employer accused me of Data breach/ Fraud and theft. Also he is sending legal notice via email. As per the client they - informed me that they have cancelled their contract with the company and they can't help me by recovering the sent items deleted data. Please advise, what I can do in this case to get my FnF, if not I don't want anything legal against me. Thanks!