What can I possibly do?
Emails stopped working.
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This is by design. Flows are stored as part of the user who created them, and by default they run under the credentials of the user as well. First, I would immediately contact your SharePoint admins and verify that the Flow has been shared with another user and get ownership transferred, as the flow itself could get deleted.
Because of the issue you raised, many shops set up a "service account", and use this service account to build flows and/or use it as the account for connections such as email.
Service account = an account where the password doesn't expire.