I agree with @cyberzork comments and with Michal’s statement that it doesn’t make business sense to put in the large engineering effort to port the software to Linux. I know other users on the forum have tried to get it to work using Wine (Make eM Run On Linux Wine), but ran into a couple issues. I think the best chance to get eM Client to run on Linux with the least engineering work would be to get it to run in Wine without errors. This would be the solution with the least effort for eM Client if they were to consider it.
Lastly, if you want eM Client to run now on Linux, then your only option would be to use something like VirtualBox to install a Windows guest to run the software.
Otherwise if you want a full port, then your only chance to get eM Client to reconsider would be for enough users to vote for it: Linux support / eM Client for Linux | Mail | eM Client