email throttling

Email throttling is a key topic in Microsoft 365 administration, particularly regarding MOERA (Microsoft Online Email Routing Address) domains. Microsoft is enforcing strict outbound throttling for organizations still using the shared onmicrosoft.com sending address, limiting external email to 100 recipients per organization in a 24-hour rolling window. This measure aims to curb abuse of newly provisioned tenants and protect the reputation of the shared domain. The throttling policy rolls out in stages starting with trial tenants in October 2025. The recommended solution is to migrate to a verified custom domain to avoid these restrictions. This tag covers the technical implications, rollout timeline, and mitigation strategies for email throttling in Microsoft 365 environments.