Short answer: never turn a provider's maximum allowance into a cold-email goal. Choose a lower operating limit, count all sending against it, and let health signals reduce usable capacity.
Three different kinds of limit
| Layer | Who sets it | What it means |
|---|---|---|
| Provider ceiling | Google or Microsoft | A service or anti-abuse boundary; crossing it can restrict sending |
| MailSequence control | Workspace operator and system safeguards | A lower cap used to distribute and stop campaign activity |
| Safe operating level | Determined from the mailbox's circumstances | The volume current authentication, history, audience, and feedback can support |
Safe operating volume changes with mailbox activity, provider responses, and campaign quality. It is usually lower than the provider ceiling.
Google Workspace limits
Google publishes sending limits that vary by account type and sending method. Its current limits page should be checked before planning capacity because limits can change and trial accounts can differ from paid accounts.
Google's sender guidelines require authentication and recommend slow, consistent volume increases. Senders above its bulk threshold to personal Gmail accounts face additional SPF, DKIM, DMARC, alignment, and unsubscribe requirements. The threshold triggers those requirements. It does not recommend a daily sending volume.
Microsoft 365 limits
Exchange Online publishes recipient-rate and message-rate ceilings. For common plans, its service description lists 10,000 recipients per day and 30 messages per minute, while tenant-level external-recipient limits and undisclosed anti-abuse controls can constrain sending further.
Microsoft also states that Exchange Online is not suited to bulk-mailing scenarios and describes outbound mass mailing as best effort. Those statements are important context: a published ceiling is not approval to send unsolicited campaigns up to that number.
How to choose an operating limit
- Start with the provider's current published rules and the organization's own policy.
- Subtract ordinary person-to-person, transactional, and other automated sending.
- Apply a lower mailbox cap based on age, sending history, and recent health.
- Apply a domain-level cap across every mailbox that shares the domain.
- Begin below those caps and increase gradually only while signals remain stable.
- Reduce or pause on authentication failures, deferrals, bounces, complaints, or unusual provider responses.
A capacity example
Five campaign inboxes can share one domain. Independent inbox allowances can create a sharp increase at the domain level. MailSequence therefore supports inbox and domain controls. Only send-ready inboxes are eligible for a campaign pool.
Rotation distributes work; it does not create additional reputation or make an unsafe total volume safe. The total across the pool still needs to fit the domain and provider context.
How MailSequence enforces capacity
MailSequence uses explicit inbox and domain limits, checks sender readiness, honors suppression decisions at send time, and can remove unhealthy or unready inboxes from campaign eligibility. Warmup and campaign activity both consume real capacity and should be planned together.
Primary sources
- Google Workspace: Gmail sending limits
Current limits by account and sending method. - Google: Email sender guidelines
Authentication, gradual volume, consistency, bulk-sender, unsubscribe, and spam-rate guidance. - Microsoft: Exchange Online limits
Recipient, message-rate, and tenant external-recipient limits, plus bulk-mailing suitability. - Microsoft: Outbound spam protection
Outbound controls, mass-mailing guidance, authentication, and list-hygiene practices.