Office 365 by default can only send emails from one email account (the account name).  Errors will occur if you try and send using the operator email address etc.

This may be able to be addressed by configuring Mailbox permissions.  Refer to the article below.  This should be carried out by the hardware technician or client.

https://docs.microsoft.com/en-us/office365/admin/add-users/give-mailbox-permissions-to-another-user?view=o365-worldwide#send-email-on-behalf-of-another-user