We believe that the slowness of the new version is likely due to the attachment indexation and folder syncing. You can try leaving eM Client running overnight so it can complete this process.

Alternatively, you can run the eM Client application with a disabled indexer by pressing the Windows key and R key at the same time and entering the following command:

"C:\Program Files (x86)\eM Client\MailClient.exe" --disable-attachment-indexer

(Unfortunately there's not currently a similar workaround for Mac OS)

We’re also working hard on fixing the speed issue and bringing you better performance with future updates.