When you log into Spark on a new device with your email for sync, the app syncs all your email accounts and preferences (swipes, signature, templates, etc.). The email for sync is the email address you used to log in to Spark for the first time. Learn more about the sync option in Spark.
The account you logged into becomes your email for sync. Now, you can add other email accounts to Spark and adjust your preferences. Spark will sync them when you sign into this account on a new device.
If you see an error message, this is most likely because you already have an account with the email address you enter as an email for sync. In this case, simply log out of Spark and log in using this email address.
Note: You can use different emails for sync on different devices. For example, you can log into your work email on your office computer while using your personal email to sync preferences across your own devices.