Welcome to the Microsoft Q&A forum.
I understand how concerning it is to see all Inbox emails disappear, especially when some of them are important and this happened shortly after purchasing Microsoft 365.
To clarify first, upgrading to Microsoft 365 or increasing mailbox storage does not remove Inbox emails from Outlook.com or Hotmail accounts. When emails disappear around the same time as an upgrade, it is usually related to how the mailbox is being displayed or synced, rather than the purchase itself.
Before escalation, it is important to confirm whether the emails still exist on the server:
- Sign in to Outlook.com using a web browser at https://outlook.live.com with the same Hotmail account.
- Check Deleted Items and, if available, use Recover items deleted from this folder (this option only works within a limited time).
- Review other folders such as Archive, Junk Email, or any custom folders to ensure messages were not moved.
- If the emails are also missing on the web, this confirms the issue is not limited to the Classic Outlook app on Windows.
If the emails are not present on Outlook.com and cannot be recovered from Deleted Items, recovery requires an account‑level review, which cannot be performed from this user‑to‑user forum.
In that case, contacting Microsoft Support directly is the appropriate next step. For personal Outlook.com or Hotmail accounts, live chat is the recommended option. You can follow these steps:
- Visit the Microsoft Support contact page: Contact - Microsoft Support
- In the search bar provided on the page, type "Outlook issue" and press Enter.
- Click on the "Get Help" button that appears.
- Scroll down the page until you see and click on the "Contact Support" option.
- When prompted to select your product or service, choose "Other Products".
- For the category, choose "Outlook".
- Look for and click on "Chat with a support agent in your web browser".
- Confirm your personal email when prompted - this is the email Microsoft will use to communicate with you during and after the support session.
- Explain your situation clearly: Be concise but provide all the relevant details.
I hope this explains what can and cannot be addressed from the forum and outlines the correct path for further assistance.