E-mail that has been migrated from the old system will appear in the Inbox of your new e-mail account but the e-mails are actually located in a subfolder of your account.
Instructions provided here demonstrate how to find old e-mails that have been migrated into the new account using a Web browser and the Outlook Web App (OWA). You must first sign into OWA in order to follow these instructions.
To find the e-mails and folders that were imported first click on More in your folder list:
Next, you will find a folder simply named user. Click the arrow next to this folder to expand its contents.
The next folder will match the first part of your e-mail address. For example, if your e-mail address is email@example.com then the folder would be named yourusername. Expanding this folder by clicking the arrow will list any folders that were migrated from the old system. E-mails that were migrated can be found within this folder and its subfolders.