eM Sync is an optional service provided by eM Client for synchronizing selected settings across desktop and mobile devices. The account and app data are protected via end-to-end encryption with zero-knowledge by the eM Client company – that means we cannot read any of the information, even if we wanted to.
In this article, we explain the basics of how eM Sync works and its security.
How does eM Sync work?
You can create a new eM Sync account or sign in to an existing one during the initial app setup or any time later in Settings > eM Sync. The logged-in eM Sync account, synchronization preferences, and password used to encrypt the data are also managed here.
Selected data is synchronized across devices signed in to the same eM Sync account.
eM Sync can synchronize account configurations (email, calendar, contacts, chat, and others), general application settings, signatures, email templates, and QuickTexts.
You can select which accounts, settings, and items to synchronize and which are to be kept locally. If you make any changes while offline or if there are any conflicts between multiple devices, you will be able to choose which ones to keep – the data is not overwritten automatically.
Is eM Sync secure?
All synchronized data is protected by zero-knowledge end-to-end encryption.
Data is encrypted on your device with an AES 256-bit symmetric key using your eM Sync account password and only uploaded to the server once encrypted.
The eM Client company or any third party (e.g., in case of any data breach) has no way of accessing the eM Sync data – only you have the means to decrypt and access it on your device using the password you created.
During the eM Sync account creation, it is required to use a password containing at least 8 characters, numbers, uppercase letters, and lowercase letters. Since this password is the only credential that can decrypt the synchronized data, it’s recommended to use a strong and unique one – the longer and more complex, the better.
eM Client cannot synchronize any user data unless you are explicitly signed in to an eM Sync account in the eM Sync settings section.
What data is stored on the eM Sync server?
eM Sync stores the data you specify (account configurations, general application settings, signatures, email templates and Quick Texts) as well as activity logs recording any changes to them; including device name, date of change and IP address.
eM Sync account credentials (email and password) are stored on the eM Sync server hosted by Microsoft Azure. User passwords are protected by AES-GCM encryption.
The data selected for synchronization and its logs are stored in a separate database on the same server.
How do I decide which settings to synchronize?
All synchronization settings are available in Settings > eM Sync.
In addition to choosing which items and existing accounts to synchronize, you can also configure whether newly added accounts are uploaded to the eM Sync server and whether accounts already stored on the server are imported to your current device.
Both options can be set to Always (performed automatically), Ask (eM Client prompts you before taking action), or Never (you manage sync settings for new accounts manually).
eM Client desktop: eM Sync settings
How to stop data synchronization?
Logging out of the eM Sync account in the eM Client app on a specific device completely stops two-way data synchronization on that device.
If you want to stop synchronizing just a specific account or information, use the options in Settings > eM Sync.
How can I request removal of my data?
If you’d like to request the deletion of your eM Sync account and/or currently synchronized data from the eM Sync servers, you can do so to via the dedicated website:
Please note that this action is permanent – once your data is removed from our servers, it’s not possible to recover it!
Can I reset my eM Sync password if I forget it?
Yes, you can reset your eM Sync password via the eM Sync password reset page. However, doing so will wipe all your synchronized data and preferences. This happens because the data is encrypted – without the original password, it cannot be decrypted, and therefore there is no way to restore it anyway.
Please keep in mind that eM Client has no way to restore your data once you forget or reset your password.