Limitations of Exchange ActiveSync
Exchange ActiveSync (EAS) is designed for synchronising emails, calendars and contacts on mobile devices and is not supported on desktop systems such as Windows or macOS. Certain limits apply depending on the data type and EAS client.
Overview of Exchange ActiveSync restrictions
With mailbox, the following data can currently be synchronised via Exchange ActiveSync:
| Data type | Time period/limit |
|---|---|
| Emails | Last 18 months |
| Calendars | Up to 3 years in the past and future |
| Contacts | No fixed limit |
| Emails per folder | Approximately 500 emails |
These figures are based on the current technical specifications of mailbox and the protocol limits of Exchange ActiveSync.
For larger data volumes or older emails, synchronisation may be restricted depending on the device or email app.
Troubleshooting synchronisation issues
Many email apps offer a setting such as “Sync Limit” or “Synchronisation Period”. Start by setting the synchronisation period on your mobile device to 1 month. A shorter period reduces the volume of data and can help prevent synchronisation errors.
If emails, calendars or contacts are missing despite selecting an appropriate synchronisation period, the cause may lie in manufacturer-specific customisations of the device, email app or EAS client you are using.
Please note that mailbox is not providing support in this regard.
Recommendation: Use open standards
For synchronising large or older data sets, as well as for desktop applications, we recommend using open standards:
- IMAP for emails
- CalDAV for calendars
- CardDAV for contacts
These standards are not dependent on the specific EAS implementation of a device or email app.
