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Sending Limits

TenantCore sending limits are infrastructure controls designed to keep mailbox sending volume within the daily limit you define. They are not deliverability guarantees and they do not replace good list hygiene.

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Default operating model

TenantCore’s outbound infrastructure is designed around a maximum of 25 sends per mailbox per day. With up to 36 mailboxes in a tenant, that provides up to:

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How enforcement works

TenantCore measures Microsoft 365 sending activity for each mailbox and compares that usage with the configured limit. At a high level:
Microsoft Exchange Online remains the final enforcement boundary, so the limit does not depend solely on the sending tool’s own daily-limit setting.

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Why this matters

A sending tool can have its own daily limit, but a provider-side setting is not the same thing as an Exchange-level control. For supported infrastructure, TenantCore keeps the Microsoft-side limit as the final boundary. You should still configure your sending tool at or below the limit you intend to enforce through TenantCore.

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Usage state

TenantCore can show mailbox utilization against the configured daily limit. This lets the operator see:
  • configured limit
  • sends observed
  • remaining capacity
  • restriction state where applicable

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BYOT behavior

For BYOT tenants, TenantCore can manage the configured sending-limit workflow without automatically taking reputation-remediation actions that are reserved for TenantCore-managed infrastructure. Reputation monitoring and send-limit configuration are separate concepts.

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Sending limits and reputation

A mailbox staying under 25 sends per day can still have poor reputation. For example:
  • high hard-bounce rate
  • spam filtering
  • poor list quality
TenantCore therefore tracks reputation signals separately from volume controls. See Monitoring & Reputation for the difference.