"The connection to your mail server timed out" error in Outlook for iOS or Outlook for Android

  • Article
  • Applies to:
    Outlook for iOS, Outlook for Android, Exchange Server 2013, Exchange Server 2010

Symptoms

When you try to sign in to your Exchange on-premises account in Outlook for iOS or Outlook for Android, you receive the following error message:

The connection to your mail server timed out.

Also, mailbox synchronization might stop unexpectedly if your Exchange account is already added to Outlook.

Cause

This issue occurs if either of the following conditions is true:

  • The version of Exchange Server that you're running uses TLS 1.1 or 1.0.
  • The version of Windows Server that's hosting the on-premises Exchange Server is version 2008 or an earlier version, and is using TLS 1.1 or 1.0.

Both TLS 1.0 and 1.1 are deprecated.

Outlook for iOS and Outlook for Android now block users from signing in to an environment that uses TLS 1.1 or 1.0. They support only versions of Exchange Server and operating system environments that use TLS 1.2 or later versions.

If your operating system currently uses TLS 1.2, the issue might be caused by an expired TLS certificate.

Resolution

Use the following guidance to enable TLS 1.2 for the Exchange Server and Windows Server in your environment.

Although Exchange Server version 2010 and later versions can be updated to enable TLS 1.2, earlier versions of Exchange Server have only the option to upgrade to a later version to be able to use Outlook for iOS or Outlook for Android.

If your environment already uses TLS 1.2 or later versions, do the following: