@Connor0967,
There are few options where you can find the old emails:
1. Check the Old Email folder in the Outlook Email Client.
This option works if you have a Microsoft Outlook app.
Go to the Folder menu tab
Click New Search Folder
Select Old email (Organizing Mail section)
Choose the period you need (e.g., older than three months).
Select the Microsoft 365 account you need.
Click OK and close the window.
Now, return to the main window where you can already see the folder named Older than 3 months in the Search Folders section. Click the folder to check all Outlook emails older than three months. Note: if you delete this folder, your emails won't be deleted.
2. Check the Cache Exchange mode setting
It is a setting in Outlook that defines the period for email storage. To check what is the current period for you, do the following:
Click File
Go to Account Settings and choose the needed account and click Change.
Check Cached Exchange Mode settings. Note: It is only available for Exchange accounts. By default, the local storage for emails works for a year. To change it, move the slider from 1 year to All. Click Next to complete the configuration and reboot Outlook.
Now, the emails shouldn't be deleted after 12 months.
Check more details about finding your old Outlook emails in our blog post https://www.nakivo.com/blog/how-to-find-old-emails-in-microsoft-365/
Let me know if you need any further assistance.