1. Click on the following link:
https://testconnectivity.microsoft.com/tests/o365
2. Click Service Account Access.
3. Complete the form.
Target mailbox email address: Enter the email address of the mailbox you wish to test.
Authentication type: Select Basic from the dropdown list.
Microsoft Account: Enter the address of your service account
Password: Enter the password of the service account
Tick the Use Exchange Impersonation button and then enter the email address of the mailbox you wish to test.
4. Complete the verification process and click Perform Test.
