How to Change Language and Regional Settings in Office 365

Microsoft 365 mailbox language and regional settings control how mailbox-specific information such as language, time zone, date and time formats, and localized default folder names are presented. If you are looking for “language settings on Office 365 server,” the setting is more accurately managed at the Exchange Online mailbox level rather than as a single server-wide language setting.

This is especially important when mailboxes use different languages. For example, a French mailbox can use Boîte de réception for Inbox, Éléments envoyés for Sent Items, and Éléments supprimés for Deleted Items. During migration, source and target mailbox languages should be reviewed and folder mapping should be validated so localized default folders are handled correctly.

This guide explains how to change the mailbox language and regional settings in Outlook on the web, how administrators can verify or update the same configuration with Exchange Online PowerShell, and what to check before migrating multilingual mailboxes.

What Office 365 language and regional settings control

Mailbox regional configuration can include the mailbox language, date format, time format, time zone, and the language used for default folders. These settings affect the mailbox experience but are separate from the language settings used by desktop Office applications.

• Mailbox language: Controls the language associated with the Exchange Online mailbox.
• Time zone: Determines the mailbox time-zone configuration used by Outlook on the web and Exchange Online.
• Date and time formats: Control how dates and times are displayed for the mailbox.
• Default folder localization: Can rename standard folders such as Inbox, Sent Items, Drafts, Junk Email, and Deleted Items to the selected mailbox language.

Office 365 mailbox language vs Office app language

Changing the mailbox language is not the same as changing the display or proofing language in Word, Excel, or the Outlook desktop application. Before changing a setting, identify which layer needs to be updated.

• Mailbox regional settings: Language, time zone, date/time formats, and default-folder localization for the Exchange Online mailbox.
• Outlook on the web language: The web Outlook interface associated with the mailbox language setting.
• Office display language: Menus and controls in desktop Office applications.
• Authoring and proofing language: Writing, spelling, and proofing tools used by Office applications.

How to change language and regional settings in Outlook on the web

1. Sign in to Microsoft 365 and open Outlook on the web.

   

2. Select the Settings icon in the upper-right corner.

   

3. In Settings, go to General and select Language and time.

   

4. Select the required language. Review the available date format, time format, and time-zone settings as needed.

   

5. If the default mailbox folders should use the selected language, enable Rename default folders so their names match the specified language.

   

6. Select Save. Refresh Outlook on the web or sign out and sign back in if the change is not immediately visible. Then verify that the language, regional formats, and default folder names match the intended configuration.

Change Office 365 mailbox language using Exchange Online PowerShell

Administrators can inspect and update mailbox regional configuration with Exchange Online PowerShell. Appropriate Exchange Online permissions are required.

1. Connect to Exchange Online

Connect-ExchangeOnline

2. Check the current mailbox regional configuration

Get-MailboxRegionalConfiguration -Identity user@domain.com

This returns mailbox regional properties such as language, date format, time format, and time zone.

3. Change the mailbox language

Set-MailboxRegionalConfiguration -Identity user@domain.com -Language en-US

Replace en-US with the required supported culture code.

4. Localize the default folder names when required

Set-MailboxRegionalConfiguration -Identity user@domain.com -Language en-US -LocalizeDefaultFolderName

Changing the language and localizing default folder names are related but distinct operations. Use folder localization only when folders such as Inbox, Sent Items, Drafts, Junk Email, and Deleted Items should be renamed to the selected mailbox language.

5. Verify the mailbox language and default folder names

Get-MailboxRegionalConfiguration -Identity user@domain.com -VerifyDefaultFolderNameLanguage | Format-List Language,DateFormat,TimeFormat,TimeZone,DefaultFolderNameMatchingUserLanguage

The DefaultFolderNameMatchingUserLanguage value helps confirm whether the default folder names are localized according to the mailbox language.

Why mailbox language matters during Office 365 migration

Localized default folder names can affect how administrators interpret source and target mailbox structures during a migration. A source mailbox and target mailbox can use different languages even when both are hosted in Microsoft 365. Matching or deliberately configuring the target mailbox regional settings, then validating folder mapping, can help prevent incorrect handling of default folders.

For example, a French source mailbox may show Boîte de réception, Éléments envoyés, and Éléments supprimés, while an English target mailbox shows Inbox, Sent Items, and Deleted Items. These are examples of localized default-folder names; changing language alone should not be treated as a guarantee that every migration workflow will map folders automatically.

When EdbMails is used for the mailbox transfer, review the source and target folder mapping before starting the migration and validate the migrated folders afterward. For the broader migration capability, see the Office 365 migration Tool.

Before migrating a mailbox with localized folders

Language and folder localization should be reviewed as part of migration preparation rather than after users report unexpected folder names. For overall project preparation, the Office 365 migration guide covers the wider migration workflow.

• Identify the source mailbox language and regional configuration.
• Check the source mailbox's default folder names.
• Check the target mailbox language, time zone, and regional settings.
• Decide whether default folders should be localized on the target.
• Confirm how the selected migration workflow maps localized source folders to target folders.
• Run a pilot migration when multiple mailbox languages are present.
• Validate folder names and migrated items after the migration.
• Use the Office 365 migration checklist to review other pre- and post-migration tasks.

Why default folder names may not change

If you change the mailbox language but the default folder names remain unchanged, check the following:

• Folder localization was not selected: Changing the mailbox language by itself does not necessarily rename existing default folders. Enable the default-folder rename option or use the PowerShell localization parameter when appropriate.
• A conflicting folder already exists: Localization can fail when the mailbox already contains another folder with the same name that a default folder would receive in the selected language. Rename the conflicting folder to a unique name, then repeat the localization.
• The mailbox view has not refreshed: Refresh Outlook on the web or sign out and sign back in. Restart Outlook desktop if you are checking folder names there.
• Administrator permissions are insufficient: Exchange Online PowerShell commands require the necessary permissions for the target mailbox.
• Source and target settings differ: During migration, verify the regional configuration on both sides instead of assuming they use the same language.

After making changes, run Get-MailboxRegionalConfiguration again and verify the mailbox language and default-folder localization before beginning a migration or troubleshooting folder-mapping behavior.