365 tenant blocked for delivery e-mails

Your business has been unable to send for two weeks despite an engineer reviewing connectors and outbound settings. First obtain the complete non-delivery report: a tenant restriction differs from an individual blocked sender. If it says 550 5.7.705, Microsoft documents that the underlying spam source must be remediated before Support removes the tenant block; changing outbound limits alone is not that removal. Have your administrator check compromised accounts and connectors, and separately review Defender’s Restricted entities page. Do not unblock an account before securing it. In the Microsoft 365 admin center, use Help & support, then Contact Support and request a phone callback, quoting the existing case and business impact. Provide recent failed-message timestamps, error codes and remediation evidence privately in the case. If all subscriptions were purchased through a partner, contact that partner for support. The community cannot remove the restriction or guarantee when Microsoft will lift it.