What is the maximum "Day Sync" of email data on Outlook Mobile app for Exchange on-premise mailboxes?

Question

We have a complete on-premises Exchange environment, after doing some research we found that outlook mobile has option to set maximum sync day of email data, but this option is available only for M365 mailbox or Hybrid Exchange with modern authentication enabled.

I cannot find any official document from Microsoft mention about the maximum sync day of email data in outlook mobile for on-premises Exchange mailbox. So, what is the max day sync supported in outlook mobile for on-premises Exchange mailboxes? Is it configurable from Exchange Server side? If possible, can give me an official document that stated about max day sync supported outlook mobile for on-premises exchange mailbox?

Answer 1

Hi @Kosal Yeang 

Thank you for posting your question in the Microsoft Q&A forum. 

Outlook for iOS and Android does not expose a configurable maximum email sync window when connecting to an on‑premises Exchange mailbox. Outlook mobile connects to on‑premises Exchange using Exchange ActiveSync (EAS)–based connectivity, but the Outlook mobile app itself does not provide a setting to control how many days of email are synchronized.

Exchange ActiveSync mailbox policies include the MaxEmailAgeFilter setting, which limits how many days of email are synchronized for EAS‑compliant clients such as native iOS Mail or Android mail applications.

However, Microsoft documentation states that Outlook for iOS and Android supports only a subset of Exchange ActiveSync mailbox policy settings, and the MaxEmailAgeFilter policy is not listed among the supported policies.

Therefore, there is no documented way to configure or enforce a maximum email sync window for Outlook mobile clients connecting to on‑premises Exchange mailboxes from the Exchange Server side.

I hope this information is helpful.

---

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".          

Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.  

Answer 2

For on-premises Exchange mailboxes accessed with Outlook for iOS and Android, the “Days of Email to Sync” setting is not supported and therefore cannot be configured from the Exchange Server side.

For basic authentication with on-premises Exchange, Microsoft explicitly lists “Sync Settings (Days of Email to Sync)” as not supported for Outlook for iOS and Android.

For hybrid Exchange with Modern Authentication, Outlook for iOS and Android uses a Microsoft 365/Office 365–based architecture and native Microsoft sync technology. In that model, the client feature “Sync Settings (Days of Email to Sync)” is also listed as not supported for on-premises mailboxes, and Outlook only supports viewing up to four weeks of email (no “Load More Messages” beyond that) for those on-premises mailboxes.

The days-based sync window that can be controlled via Intune app configuration (com.microsoft.outlook.Settings.DaysToSync, 1–90 days) applies to Outlook for iOS and Android when used with Exchange Online mailboxes (Microsoft 365/Office 365), not to purely on-premises Exchange mailboxes.

So for a complete on-premises Exchange environment:

• There is no configurable maximum “Day Sync” value on the server side for Outlook mobile.
• The Days of Email to Sync feature is not supported for those on-premises mailboxes.
• In the hybrid Modern Auth scenario, on-premises data synchronized into Exchange Online for Outlook mobile is limited to four weeks of email and cannot be extended via a server-side setting.

---

References:

• Using Basic authentication with Outlook for iOS and Android
• Using hybrid Modern Authentication with Outlook for iOS and Android
• Deploying Outlook for iOS and Android app configuration settings in Exchange Online
• Outlook for iOS and Android in Exchange Online