Filing a case against ex-employee for defamation

Hi,

Please note that I am the business owner of a Free Zone company (Ajman, UAE). I was successfully running the business for the last 3 years.

Unfortunately, one of my ex-employees who left us 6 months back has made access to our free zone portal using our password from outside, downloaded some employment contracts, payrolls and sent a big list of false allegations against me and my company to defame us and spoil the reputation of the company.

The ex-employee has sent these messages through his personal Whatsapp number to the COO of our USA-based buyer. He sent all these documents and made false allegations about me, my staff, and my family in person to defame me in front of our prime US customer.

A team member of the US buyer has emailed me and Whatsapped me these details to do an enquire about the facts. Is there anything I can do legally to ex-employee?

All I have is the Whatsapp messages and emails from my buyer regarding these things. The ex-employee is running his business in Dubai.