OUMail is a student email service, so generally, OUMail accounts (email addresses) are not issued to faculty and staff, except for some teachers who need to teach how to use OUMail. However, if you need an OUMail account to use the integration features between the CLE (Classroom Learning Environment) and Microsoft Teams, please apply through the application form.
(Reference) Starting October 21, 2022, part-time lecturers and contract lecturers, and starting February 1, 2023, invited faculty and invited researchers have access to ICHO services (which provide an email address ending in @osaka-u.ac.jp and access to OneDrive and other services). Please consider using this service as well.