EdbMails EDB Recovery and Migration software
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    EdbMails
    All-in-one Recovery and Migration
    • EDB Recovery and Migration
    • OST, PST, MBOX, NSF, EML, MSG
    • Office 365, Exchange Migration
    • SharePoint, OneDrive & Teams
    • Google Workspace Migration
    • IMAP Migration
    • Duplicate Remover
    • EdbMails Data Recovery
    • Backup Solutions
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    EDB Recovery and Migration

    EdbMails lets you recover corrupted, damaged, and offline Exchange EDB files, convert EDB mailboxes to PST format, and directly migrate mailbox data to Office 365 and live Exchange Server.

    EDB to PST
    EDB to PST
    Recover corrupted, damaged, offline EDB files and convert Exchange EDB mailboxes to PST file format
    Public Folder to Exchange
    Public Folder to Exchange
    Migrate public folders from an Exchange offline EDB file to live Exchange Server
    EDB to Live Exchange Migration
    EDB to Live Exchange Migration
    Directly migrate offline Exchange database (EDB) files to live Exchange server
    Archive Mailbox to Office 365
    Archive Mailbox to Office 365
    Migrate archive mailboxes from offline EDB files directly to Office 365
    EDB to Office 365 Migration
    EDB to Office 365 Migration
    Directly migrate offline Exchange database (EDB) files to Office 365
    Public Folder to Office 365
    Public Folder to Office 365
    Migrate public folders from an offline Exchange EDB file to Office 365

    OST, PST, MBOX, NSF, EML, MSG Export and Migration

    EdbMails lets you to recover OST and PST files, export OST, PST, MBOX, NSF, EML, and MSG files to PST files, and directly migrate OST, PST, MBOX, and NSF mailbox data to Office 365 and live Exchange Server.

    OST Recovery and Migration
    OST Recovery and Migration
    Recover offline OST files, convert OST to PST, and migrate OST to Office 365 and Exchange Server
    PST Recovery and Migration
    PST Recovery and Migration
    Recover Outlook PST files , Export PST to PST, migrate PST to Office 365 and Exchange Server
    MBOX Export and Migration
    MBOX Export and Migration
    Export MBOX to PST, migrate MBOX to Office 365 and Exchange Server
    NSF Export and Migration
    NSF Export and Migration
    Export NSF to PST, migrate NSF to Office 365 and Exchange Server
    EML to PST Export
    EML to PST Export
    Convert EML files to Outlook PST files
    PST to MSG Export
    PST to MSG Export
    Convert Outlook PST file to MSG file format
    MSG to PST Export
    MSG to PST Export
    Export MSG files to Outlook PST files

    Office 365, Exchange Migration

    EdbMails lets you securely migrate mailboxes across Microsoft 365, Exchange, Google Workspace (Google Workspace Migraton), and IMAP-supported servers such as Outlook, Gmail, Zimbra, Zoho Mail, and cPanel, ensuring zero downtime.

    Office 365 Backup
    Office 365 Migration
    Migrate between Office 365 tenants, Office 365 to Exchange, Office 365 to PST, PST files to Office 365.
    Exchange Server Backup
    Exchange Migration
    Migrate between any Exchange Servers, Exchange to Office 365, Exchange to PST, PST files to Exchange.
    Tenant to Tenant Migration
    Tenant to Tenant Migration
    Migrate Mailboxes, Public Folders, Archive Mailboxes between Office 365 Tenants.
    Exchange to Office 365
    Exchange to Office 365
    Migrate Mailboxes, Public Folders, Archive Mailboxes from live Exchange server to Office 365.
    Office 365 to IMAP
    Office 365 to IMAP
    Migrate Office 365 to IMAP, Office 365 to Gmail, Office 365 to Outlook, Office 365 to Zoho etc.
    Exchange to IMAP
    Exchange to IMAP
    Migrate from live Exchange Server to IMAP servers such as Gmail, Outlook, and Zoho Mail.
    Public Folder to Office 365
    Public Folder to Office 365
    Migrate Public Folders between Office 365 tenants with complete folder hierarchy and mailbox data integrity.
    Exchange to PST
    Exchange to PST
    Export live Exchange Server mailboxes, public folders, and archive mailboxes to Outlook PST files.

    SharePoint, OneDrive & Microsoft Teams Migration

    EdbMails lets you migrate SharePoint sites, OneDrive data, Microsoft Teams, teams, channels, chats, permissions, and documents between Microsoft 365 tenants while maintaining the existing folder structure and data integrity.

    SharePoint, OneDrive & Teams Backup
    SharePoint Online Migration
    Migrate documents, lists, files and folders from SharePoint sites.
    OneDrive for Business Migration
    OneDrive for Business Migration
    Migrate documents, lists, files, folders, private chats from OneDrive.
    Microsoft Teams Migration
    Microsoft Teams Migration
    Migrate Teams, chats, channels, documents, files and folders etc.

    Google Workspace / G Suite Migration

    EdbMails offers secure Google Workspace migration to Office 365, Exchange, or IMAP, and export to PST covering emails, contacts, calendars and tasks.

    Google Workspace Migration
    Google Workspace Migration
    Migrate emails, calendars, contacts, tasks from Google workspace to Google workspace, office 365, Exchange and IMAP. Export to PST
    Google Workspace to Office 365
    Google Workspace to Office 365
    Migrate emails, calendars, contacts, tasks from Google Workspace / G Suite to Office 365
    Google Workspace to Exchange Server
    Google Workspace to Exchange Server
    Migrate emails, calendars, contacts, tasks from Google Workspace / G Suite to on-Premise Exchange Server
    Google Workspace to IMAP
    Google Workspace to IMAP
    Migrate emails, calendars, contacts, tasks from Google Workspace / G Suite to IMAP, Outlook, Zimbra, Zoho etc.
    Google Workspace to Google Workspace Migration
    Google Workspace to Google Workspace
    Migrate emails, calendars, contacts, tasks between two Google Workspace / G Suite tenants
    Google Workspace to PST
    Google Workspace to PST
    Export emails, calendars, contacts, tasks from Google Workspace / G Suite to Outlook PST files

    IMAP Migration

    EdbMails IMAP Migration tool lets you easily migrate emails from IMAP servers such as Outlook, Gmail, Zoho Mail, Zimbra, cPanel, and more. Supports IMAP to IMAP, Office 365, Exchange Server, PST, and bulk PST to IMAP migration.

    IMAP Email Backup & Migration
    IMAP Email Backup & Migration
    Backup and migrate emails from IMAP servers to PST, Office 365, and On-Premises Exchange Server
    IMAP to Office 365
    IMAP to Office 365
    Migrate emails, folders, and attachments from IMAP servers to Office 365
    IMAP to Exchange
    IMAP to Exchange
    Migrate emails, folders, and attachments from IMAP servers to on-premises Exchange Server
    IMAP to PST
    IMAP to PST
    Export emails, folders, and attachments from IMAP servers to Outlook PST files for backup
    PST to IMAP
    PST to IMAP
    Migrate emails, folders, and attachments from bulk PST files to IMAP servers

    Duplicate Remover

    EdbMails Duplicate Remover lets you easily remove duplicate items from Office 365 and Exchange Server, and from IMAP, Outlook, Gmail, Zimbra, Zoho Mail, etc., ensuring a clean and organized mailbox.

    Remove Duplicates
    Remove Duplicates
    Easily clean up your Office 365, Exchange, Outlook and IMAP accounts by removing duplicate emails.
    Remove Duplicates from Office 365
    Remove Duplicates from Office 365
    Remove duplicate emails, calendars, contacts, journal tasks, etc. from Office 365.
    Remove Duplicates from Exchange Server
    Remove Duplicates from Exchange Server
    Remove duplicate emails, calendars, contacts, journal tasks, etc. from live Exchange Server.
    Remove Duplicates from IMAP, Outlook
    Remove Duplicates from IMAP, Outlook
    Remove duplicate emails, attachments from IMAP, Outlook, Gmail, Zimbra, Zoho Mail etc.

    Exchange, SharePoint, OneDrive, Teams and Office 365 Backup

    EdbMails enables secure, automated backup and recovery for Microsoft 365 services including Exchange Online, SharePoint, OneDrive, Teams, and Live Exchange Server with complete data protection and restore flexibility.

    Office 365 Backup
    Office 365 Backup
    Incremental, Granular, Encrypted and Compressed Office 365 Mailboxes Backup
    Exchange Server Backup
    Exchange Server Backup
    Incremental, Granular, Encrypted and Compressed Exchange Mailboxes Backup
    SharePoint, OneDrive & Teams Backup
    SharePoint, OneDrive & Teams Backup
    Backup Online site collections, Team sites, Office 365 groups, all documents etc.

    EdbMails Data Recovery

    EdbMails Data Recovery Software lets you recover permanently deleted data, including photos, videos, documents, and archived files, from partitions on hard drives, SSDs, USB drives, SD cards, and external storage devices.

    EdbMails Data Recovery
    EdbMails Data Recovery
    Recover and restore permanently deleted data from hard drives, SSDs, USB drives, SD cards, and etc.
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User’s Manual
Office 365 Migration Tool

User Manual

User Manual

  • Office 365 Migration Tool Overview
  • What is Office 365 Migration?
  • System Requirements
  • Migration Scenarios
  • Software Setup
    • EdbMails Installation Process
    • Upgrading the Software
  • Understanding the Application
    • Software's Main Components
    • Understanding the Migration
  • FAQ
    • General
    • Migration Free Trial / Demo
    • Migration License
    • Before Migration
    • Migration - Steps
    • After Migration
  • Videos
    • Office 365 to Office 365
    • Office 365 to Exchange
    • Office 365 to IMAP
    • Office 365 to PST
    • Public Folder to Office 365
    • Archive Mailbox to Office 365
    • Public Folder to Exchange
    • Archive Mailbox to Exchange
    • Restore Bulk PST files to Office 365
    • Automatically Create Office 365 Mailboxes
    • Export Office 365 user to CSV file
  • Screenshots
    • Office 365 to Office 365
    • Office 365 to Exchange
    • Office 365 to PST
  • How it works?
    • Office 365 to Office 365
    • Office 365 to Exchange
    • Office 365 to IMAP
    • Office 365 to PST
    • Public Folder to Office 365
    • Public Folder to Exchange
    • Public Folder to Shared Mailbox
    • Archive Mailbox to Office 365
    • Archive Mailbox to Exchange
    • Office 365 to Hosted Exchange
    • Multiple PST to Office 365
    • Office 365 to Gmail Migration
    • Office 365 Shared mailbox to Exchange
    • Office 365 Public folders to PST
    • Office 365 archive mailbox to PST
    • Office 365 Shared mailbox to PST
    • Office 365 shared mailbox to Public folder
    • Office 365 Archive mailbox to Shared mailbox
    • Office 365 Shared mailbox to Archive mailbox
  • Connect to source Office 365
  • Connect to target Office 365
  • Modern Authentication Using OAuth 2.0
    • Microsoft 365 modern authentication
    • Automatic Registration
    • Manual Registration
  • Connect to Exchange server
  • Knowledge Base
    • Migrate between Office 365 tenants
    • Migrate Office 365 mailbox
    • Public folder migration
    • Office 365 Migration with same Domain
    • Office 365 Group Migration
    • Selective Mailbox Migration
    • Migration to Exchange 2007, 2010, 2013, 2016 and 2019
    • User-Defined Mailbox/Folder Mapping
    • Export Office 365 users to CSV
    • GoDaddy to Microsoft 365 migration
    • Rackspace to Office 365 migration
    • Office 365 migration methods
    • Office 365 migration checklist
    • Migrate Shared mailbox to Office 365
    • Office 365 migration best practices
    • Office 365 migration challenges
    • Convert shared mailbox to regular mailbox
    • Office 365 to Exchange 2019 migration
    • Office 365 multiple mailbox migration
    • Office 365 Server to Server Migration
    • Cross-Tenant Office 365 migration
    • Office 365 to iCloud migration
    • Office 365 to Yahoo Mail migration
    • Office 365 to cPanel Migration
    • Office 365 to SmarterMail Migration
    • Office 365 to IceWarp migration
    • Create an Office 365 Migration Endpoint
    • Validate Office 365 Mailbox Migration
    • Office 365 Migration Network Requirements
    • Microsoft 365 Migration URLs & Endpoints
    • Office 365 Migration Firewall Ports
    • DNS Changes After Office 365 Migration
    • Autodiscover Troubleshooting After Migration
    • Post-Migration MX Record Validation
    • Office 365 Mail Flow Troubleshooting
    • Mailbox Permission Validation
    • EdbMails vs CodeTwo vs MigrationWiz vs Native Tools
    • Calendar Permission Migration Issues
    • Folder Permission Troubleshooting
    • Large Mailbox Migration Best Practices
    • Archive Mailbox Sync Issues
    • Office 365 Migration Coexistence
    • Cross-Tenant Mailbox Permissions
    • Cross-Tenant Calendar Migration
    • Migration Using App-Only Authentication
    • Office 365 Mailbox Mapping Errors
    • Exchange Online Migration Limits
    • Mailbox Integrity After Migration
    • Security Best Practices for Migration
  • Migration Types
    • Cutover Migration
    • Staged Migration
  • Set Exchange Server Impersonation rights
  • Map the Mailboxes
  • Migration Walkthrough
    • Office 365 tenant to tenant migration
    • Office 365 to PST Export
  • Multifactor Authentication
    • Enable MFA in Office 365
    • Create App password for MFA
    • Disable Security Defaults
  1. Home
  2. Office 365 Migration Tool
  3. Fix ‘Mailbox does not exist’ error in Microsoft 365
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Fix ‘Mailbox does not exist’ error in Microsoft 365

In order to solve the Microsoft 365 “mailbox does not exist“ error, you must know how a mailbox is created and also how it is attached to a particular Microsoft account through Exchange Online. When a user is created and granted a license in Microsoft 365, a mailbox is created in the background.

But, if the process doesn’t complete, gets interrupted or is slightly out of sync, you may have a user account but the mailbox for that account is not ready to be delivered. This is when you get the “mailbox does not exist” error when using Outlook, Outlook Web App (OWA), PowerShell or using migration tools.

This happens often in user onboarding, directory sync on hybrid, mailbox migration, etc. In the most frequent scenario, the system fails to find an active mailbox for the user account due to problems with provisioning or synchronisation.

Put in its very simplest form: the user exists, but the mailbox wasn’t created, didn’t fully sync, or was not recognised by Exchange Online. Understanding this point will guide troubleshooting efforts to licensing, synchronisation, mailbox GUID validation, and mailbox provisioning instead of client-side issues.

Common Error Messages

  • Mailbox does not exist
  • Failed to resolve mailbox name

How to Assign a Microsoft 365 License

  1. Login to the Microsoft 365 admin center.
  2. Go to ‘Users’ and select ‘Active users’ from the left panel.

    Accessing active users

  3. Choose the user account you want to license.
  4. From the 'Licenses and Apps' tab, check all of the license options you would like. Ensure that the selected plan has Exchange Online. For example, choose 'Microsoft 365 E5 Developer'.
  5. Click 'Save changes'.

    Assigning Office 365 license

  6. If needed, open the Apps section and enable only ‘Exchange Online’ by selecting its checkbox.

    Enable Exchange Online plan

  7. Click 'Save changes' to apply them.

     You can now continue with your migration process. Changes may take time to sync across the Microsoft 365 environment. If the error still appears, wait a bit and reconnect to Microsoft 365 again.

Mailbox Provisioning Delay After License Assignment

Even after a Microsoft 365 license is assigned, the mailbox may not be immediately ready because Microsoft 365 creates the mailbox in the background. If the ‘mailbox does not exist’ error appears, EdbMails recommends allowing time for the changes to synchronize and reconnecting to Microsoft 365 before continuing. In hybrid environments, Azure AD Connect synchronization can also affect mailbox availability and should be reviewed when troubleshooting synchronization issues.

Verify Mailbox Provisioning Status

To confirm whether the mailbox has finished provisioning, go to the Microsoft 365 admin center, select ‘Users’ > ‘Active users’, and check that the user shows a mailbox under Product licenses. In the Exchange admin center, the account should also appear under ‘Recipients’ > ‘Mailboxes’; if it's missing from that list but present in Active users, provisioning has not completed. Administrators with PowerShell access can confirm this directly with Get-Mailbox -Identity <user> and check for a valid ExchangeGuid value.

Frequently Asked Questions

  1. Why does the ‘mailbox does not exist’ error appear right after I assign a license?

    When a user is created and assigned a Microsoft 365 license that includes Exchange Online, the mailbox is created in the background. If mailbox provisioning does not complete, is interrupted, or is not fully synchronized, Microsoft 365 may have the user account, but the mailbox may not yet be ready. This can result in the ‘mailbox does not exist’ error.

  2. Does this ‘mailbox does not exist’ error mean the user's data was lost?

    No. The ‘mailbox does not exist’ error indicates that the mailbox may not have been created, fully synchronized, or recognized by Exchange Online. EdbMails identifies mailbox provisioning and synchronization as possible causes of this error.

  3. Can a hybrid directory sync delay cause this error?

    Yes. EdbMails identifies directory synchronization in a hybrid environment as one of the situations where the ‘mailbox does not exist’ error can occur. If the mailbox is not fully synchronized or recognized by Exchange Online, the error may appear.

  4. How do I confirm the mailbox actually exists?

    First, verify that the user has a Microsoft 365 license that includes Exchange Online. EdbMails recommends checking the user's license settings and ensuring that Exchange Online is enabled. After applying the license, allow time for the Microsoft 365 changes to synchronize. If the error continues, wait and reconnect to Microsoft 365 again before continuing the migration.


Additional Resources:

  • How to Batch Create Outlook Profiles with Intune
  • Microsoft 365 Sign-in Window Not Displaying
  • How to Use App Passwords with EdbMails Office 365 Login
  • Steps for Manual registration of EdbMails in Azure AD
  • Office 365 Mailbox Mapping Errors
  • Automatic Creation of Mailboxes
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