Q: Can Microsoft Teams be used in China?
A: Yes. Microsoft Office 365 tenants hosted outside of China are accessible from within China. Services under Office 365 are not blocked by consumer firewall or ISPs at this time.
Users' experience may vary by service and network as Microsoft has no control over consumer internet services. They are advised to download client apps (instead of using web-based client).
If your users experience network performance issues, they should report this to NUS IT Care for troubleshooting, who can then escalate to Microsoft support.