The error message "we couldn't find a work or school account with that email address" indicates that the new Outlook is unable to locate a valid Microsoft 365 work or school account associated with the email address you are trying to use. Since you mentioned that you are using AWS WorkMail, it's important to note that the new Outlook for Windows primarily supports Microsoft 365 work and school accounts, along with other specific email providers like Outlook.com, Gmail, and Yahoo.
AWS WorkMail, being a separate service, may not be recognized as a supported account type in the new Outlook. Therefore, you might encounter issues when trying to set it up as a work or school account in Outlook.
To resolve this, you may want to check if your AWS WorkMail account can be configured using IMAP or POP settings in Outlook, as these protocols are generally supported for non-Microsoft email services. Alternatively, you could consider using the AWS WorkMail web interface or an email client that fully supports AWS WorkMail.