Bulk Add Users to a Mail-enabled Security Group

Purpose
 Reference guide for adding members to a Mail-enabled Security Group in Exchange Online.

Important Note

Microsoft Entra Admin Center does not currently support CSV bulk import for Mail-enabled Security Groups. Use Exchange Online PowerShell for bulk additions.

Prerequisites

• Exchange Administrator or Global Administrator role
• Exchange Online PowerShell module installed
• CSV containing EmailAddress column

CSV Format

EmailAddress
user1@contoso.com
 user2@contoso.com

Procedure

1. Open PowerShell as Administrator.
2. Run: Connect-ExchangeOnline
3. Save CSV as C:\Temp\Users.csv
4. Run:
    Import-Csv "C:\Temp\Users.csv" | ForEach-Object { Add-DistributionGroupMember -Identity "MailSecurityGroup" -Member $_.EmailAddress }
5. Verify:
    Get-DistributionGroupMember "MailSecurityGroup"

Entra Admin Center

Navigate to Identity > Groups > All Groups > select the Mail-enabled Security Group > Members. Only manual Add members is available; CSV import is not supported.

Troubleshooting

• Verify email addresses exist.
• Ensure sufficient admin permissions.
• Confirm the group is a Mail-enabled Security Group.
• Reconnect to Exchange Online if session expires.