erased sent and received email! how to get it back???

I am desperately
trying to retrieve sent and received email from our business email address that a recently let go employee erased.  Our emails were through eM Client email program.  We have Bell internet and a Bell email address. I have been trying all week without success from our IT Company who hosts our programs and info remotely.  I have also gotten nowhere with Bell who our email address is from.   The email address from our business was

All emails, inbox, sent items; contact lists etc have been erased from Jan 26, 2018 and previous. 

Can someone please contact me as retrieving this information is critical not only to the operation of our day to day business but it may have some critical information on why the email was erased in the first place.  We had let this employee go for cause.