Is there a way to change O365 group email address using powershell

Hi Susan,
Yes It is possible, you can add new email ID and you can promote your new Email ID as an SMTP and you can remove your Old Email ID. But performing this steps, you need a global Administrator access.

Please follow below Steps to change Office 365 group Email address:-

Current SMTP address :- WORD@mail.com
Required SMTP address :- word@mail.com

Follow the below steps in power shell using Global Administrator Credentials,

1. Connect to Exchange Online via Power shell using Global Administrator Credentials and run the below commends. First two command run separately.

Set-ExecutionPolicy Unrestricted

Start-service winrm

Import-module MSOnline
$UserCredential = Get-Credential
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
Import-PSSession $Session
Connect-MsolService -Credential $UserCredential

2. Run the below command to add required SMTP address as an alias.
Set-UnifiedGroup -Identity "X" -EmailAddresses: @{Add ="Y"}
here X is the Display Name of Office 365 group and Y is the required Email ID.
Eg:- Set-UnifiedGroup -Identity "Test o365Group" -EmailAddresses: @{Add ="WORD1@mail.com"}

3. Promote alias as a primary SMTP address,
Set-UnifiedGroup -Identity "Test O365Group" -PrimarySmtpAddress "WORD1@mail.com"

4. Remove first ID using below command.
Set-UnifiedGroup -Identity "Test o365Group" -EmailAddresses: @{Remove="WORD@mail.com"}

5. Again Add required Email Address
Eg:- Set-UnifiedGroup -Identity "Test o365Group" -EmailAddresses: @{Add ="word@mail.com"}

6. Promote alias as a primary SMTP address,
Set-UnifiedGroup -Identity "Test O365Group" -PrimarySmtpAddress "word@mail.com"

7. Remove first ID using below command.
Set-UnifiedGroup -Identity "Test o365Group" -EmailAddresses: @{Remove="WORD1@mail.com"}

Please note, For updating the Office 365 group SMTP address required Global Administrator access.Hope this will help you and let me know if you are facing any issue on this.

Thanks and Regards,
Yahkoob Ayappally