Hi MAMIDI Anjali ,
Thank you for reaching out on Microsoft Q&A!
Did you set the required 'Send as' or 'Send on behalf of' permissions, as stated in the connector definition? This is necessary before you're able to send e-mail from a distribution list.
The link referred to is found below:
https://learn.microsoft.com/en-us/office365/admin/manage/send-email-as-distribution-list
The entire MS Learn documentation for the Outlook 365 Connector can be found here:
https://learn.microsoft.com/en-us/connectors/office365connector/
Please click “Accept answer” if you find this helpful. Feel free to drop additional queries in the comments below!
Kind regards,
Sonny