Shared Mailbox Migration Guide: Transfer Team Mailboxes Successfully
Comprehensive guide to migrating shared mailboxes between email platforms. Learn how to transfer shared mailboxes, configure permissions, and maintain team collaboration during migration.
What is a Shared Mailbox?
A shared mailbox is an email account that multiple users can access to read and send messages. Common examples include support@company.com, sales@company.com, or info@company.com. Unlike distribution lists, shared mailboxes allow team members to see all emails and responses, making them ideal for collaborative work.
Common Use Cases for Shared Mailboxes
- Customer Support: support@, help@, service@
- Sales Teams: sales@, inquiries@, quotes@
- General Information: info@, contact@, hello@
- Department Mailboxes: hr@, finance@, marketing@
- Project Teams: project-name@, team-name@
Shared Mailbox Migration Challenges
Permission Complexity
Shared mailboxes have complex permission structures with different access levels (Full Access, Send As, Send on Behalf). These permissions must be carefully recreated in the new system.
Multiple Users
Multiple team members access shared mailboxes simultaneously. Migration must not disrupt their workflow or cause confusion about which system to use.
Historical Data
Shared mailboxes often contain years of important correspondence. All historical emails, sent items, and folder structures must be preserved during migration.
Send As Permissions
Users need ability to send emails as the shared mailbox address. Configuring these permissions correctly is critical for maintaining professional communication.
Pre-Migration Planning
Inventory All Shared Mailboxes
Create a comprehensive list of all shared mailboxes in your organization:
| Mailbox Address | Purpose | Size | Users |
|---|---|---|---|
| support@company.com | Customer Support | 15 GB | 8 |
| sales@company.com | Sales Inquiries | 8 GB | 5 |
| info@company.com | General Info | 3 GB | 3 |
Document Current Permissions
For each shared mailbox, document who has access and their permission levels:
# Example permission documentation
support@company.com:
- john@company.com: Full Access, Send As
- jane@company.com: Full Access, Send As
- manager@company.com: Full Access, Send As, Send on Behalf
Identify Dependencies
Document any systems or workflows that depend on shared mailboxes, such as ticketing systems, CRM integrations, or automated email processing.
Microsoft 365 Shared Mailbox Migration
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Method 1: Using Microsoft Migration Tools
Create Shared Mailboxes in Microsoft 365
In Microsoft 365 Admin Center:
- Go to Teams & groups → Shared mailboxes
- Click Add a shared mailbox
- Enter mailbox name and email address
- Add members and set permissions
Configure Permissions
Set up three types of permissions:
Full Access
Allows user to open and read all emails in the shared mailbox
Send As
Allows user to send emails as the shared mailbox address
Send on Behalf
Sends emails showing "User on behalf of Shared Mailbox"
Migrate Data Using Exchange Admin Center
Create migration batch for shared mailboxes:
- Go to Exchange Admin Center → Migration
- Create new migration batch
- Select migration type (IMAP, Cutover, or Staged)
- Include shared mailbox addresses in CSV file
- Start migration
Method 2: Using PowerShell
# Connect to Exchange Online
Connect-ExchangeOnline
# Create shared mailbox
New-Mailbox -Shared -Name "Support Team" -DisplayName "Support Team" -Alias support
# Add Full Access permission
Add-MailboxPermission -Identity support@company.com -User john@company.com -AccessRights FullAccess -InheritanceType All
# Add Send As permission
Add-RecipientPermission -Identity support@company.com -Trustee john@company.com -AccessRights SendAs
# Add Send on Behalf permission
Set-Mailbox -Identity support@company.com -GrantSendOnBehalfTo john@company.com
Google Workspace Shared Mailbox Migration
Google Workspace uses "Collaborative Inboxes" (Google Groups) instead of traditional shared mailboxes. The migration process is different but achieves similar functionality.
Create Google Group as Collaborative Inbox
In Google Admin Console:
- Go to Directory → Groups
- Click Create group
- Enter group email (e.g., support@company.com)
- Select Collaborative Inbox as group type
- Add members
Configure Group Settings
Set appropriate permissions:
Who can post: Group members
Who can view conversations: Group members
Who can view members: Group members
Allow external members: No (usually)
Migrate Data Using Google Data Migration Service
In Google Admin Console:
- Go to Data migration
- Select migration source (Exchange, IMAP, etc.)
- Map source shared mailbox to Google Group
- Start migration
Important Difference: Google Groups vs Shared Mailboxes
Google's Collaborative Inboxes work differently from traditional shared mailboxes:
- Emails appear in group interface, not in Gmail inbox
- Members can assign conversations to specific people
- Conversations can be marked as resolved
- Better for team collaboration, different workflow
Best Practices for Shared Mailbox Migration
Pro Tips for Success
Before Migration
- Document all permissions thoroughly
- Clean up old emails to reduce size
- Test with one shared mailbox first
- Notify all users of migration schedule
- Create detailed permission mapping
During Migration
- Migrate during low-activity periods
- Keep old mailbox accessible temporarily
- Verify permissions immediately after setup
- Test send/receive functionality
- Monitor for delivery issues
Post-Migration Verification
Verification Checklist
All Emails Migrated
Compare item counts between old and new mailboxes
Permissions Configured Correctly
Test each user's access level and send permissions
Folder Structure Preserved
Verify all folders and subfolders migrated correctly
Send As Works
Test sending emails as the shared mailbox address
External Email Delivery
Send test emails to external addresses and verify delivery
User Training Complete
Ensure all team members know how to access and use new mailbox
Common Issues and Solutions
Users Can't Access Shared Mailbox
Problem: Users report they can't see or access the shared mailbox.
Solution: Verify Full Access permissions are granted. In Outlook, users may need to manually add the shared mailbox: File → Account Settings → Change → More Settings → Advanced → Add.
Can't Send As Shared Mailbox
Problem: Users can read emails but can't send as the shared mailbox address.
Solution: Grant Send As permission using PowerShell or Exchange Admin Center. Note: It can take up to 60 minutes for Send As permissions to take effect.
Missing Sent Items
Problem: Sent items from shared mailbox don't appear in Sent Items folder.
Solution: Configure mailbox to save sent items in shared mailbox's Sent Items folder: Set-Mailbox -Identity shared@company.com -MessageCopyForSentAsEnabled $True
Incomplete Data Migration
Problem: Not all emails migrated from old shared mailbox.
Solution: Check migration logs for errors. Common causes: mailbox size limits, corrupted items, or permission issues. Re-run migration for failed items or use PST import for stubborn data.
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