Lost Admin -Email issues XXXXX@ourit.support

Our It admin left (and us in the lurch), we used to get emails generated when new incident was created when on local exchange from XXXXX@ourit.support. migrated to 365, now we no longer get emails?, the new It Dept. changed or added an integrated outgoing email (said there was non) with smtp.office365.com as host, but does not work. I can get it to work from the new email, but not from the centrixdental@ourit.support