Once you enable the automatic periodic backup and save settings, it will normally create a dated backup.zip file in your specified backup folder within the next 24 hours as per the task scheduler.
If it doesn’t appear or you need to modify the backup schedule and you have Windows, see the following thread on the subject…
what to do to manually create a backup
To do a manual backup, click “Menu / Backup” (Pc) or “File / Backup” (Mac). You can see when the backup is complete in Show Operations via clicking the drop-down on the right of Refresh top left. You will th n see the backup zip appear after that once completed.
Also, will the backup contain everything - mail in folders, contacts, calendar?
Yes it backs up everything within eM Client.