In eM Client 9, we introduced options for limited time synchronization. You can leave your message sync time period to All time or limit it to different time periods, from the last day to the last year.

You can set the time period individually for each of your accounts in Menu > Accounts on Windows and eM Client > Accounts on MacOS where you select the IMAP or Exchange Web Services tab, depending on the account.

We go into more detail and explore the benefits of limited time sync on our blog: Limited time sync