What happens when you exceed the limit
Sending blocked temporarily; repeated hits can suspend the account. That is the documented behavior. The undocumented one matters more: a mailbox that repeatedly runs into its cap is behaving the way Outlook.com's filters expect a bulk sender to behave, and the reputation cost outlasts the block. Treat the published figure as a ceiling to stay well under, not a daily target.
How the limit interacts with a warmup ramp
The 1,000 first-time-recipient cap is the one cold senders hit. A warmup ramp and a provider cap are two different ceilings. The cap is where Outlook.com stops you; the ramp is where reputation would stop you first. MailStrike's default ramp climbs to 30 warming emails a day per mailbox over 21 days, and real outreach starts at 20 to 30 a day once the ramp is done. Against Outlook.com's 5,000 recipients per day, the ramp never comes close; the cap is not the constraint, reputation is. Set the provider, the domain's age and the target volume below to see the schedule.
| Outreach a day, per mailbox | 1 mailbox | 2 mailboxes | 3 or more |
|---|---|---|---|
| Not sending yet | 30 | 21 | 18 |
| 10 emails | 30 | 21 | 18 |
| 20 emails | 25 | 18 | 15 |
| 30 emails | 20 | 14 | 12 |
| 40 emails | 15 | 11 | 9 |
| 50 emails | 10 | 7 | 6 |
The rule behind the table: a mailbox on its own that is not sending yet warms at the plan default of 30 a day, and once outreach starts it drops one warming email for every two you send, down to a floor of 10. Put a second mailbox on the domain and each one needs 70% of that figure, three or more and each needs 60%, because the domain earns the signal across all of them. Volume is a setting per mailbox, so you can dial these in directly.
The full setup for this provider, from the connect to the day the dashboard says the mailbox is safe to send from, is on the Outlook.com warmup page.
Trial, free tier and new-account restrictions
new/free accounts get lower temporary quotas. New accounts and trials sit under tighter limits because they have no history, which is the same reason receivers distrust them. A ramp that respects the lower limit is also the ramp that builds the history.
The bounces these limits produce
Going over a limit shows up as a bounce, not a warning. The rate-limit codes from Microsoft in the bounce code decoder, each with its message and the fix:
- 550 5.7.233: tenant external recipient limit
- 550 5.7.236: onmicrosoft.com daily limit
- 550 5.2.2: submission quota exceeded
The bulk sender rules are a separate limit
None of the caps above is the line that decides placement. Google's and Yahoo's bulk-sender requirements and Microsoft's 2025 high-volume rules set authentication, spam-rate and unsubscribe conditions that apply well below any sending cap; the sender requirements page has them provider by provider, and the auth checker tests a domain against them.
How Outlook.com compares
documented cap per day (log scale); basis differs per provider
- Zoho Mail sending limits
- Yahoo Mail sending limits
- iCloud Mail sending limits
- Amazon SES sending limits
- SendGrid sending limits
- Mailgun sending limits
Questions about Outlook.com sending limits
What is the Outlook.com sending limit per day?
5,000 recipients/day; 1,000/day to first-time (non-relationship) recipients. Recipients per day: 5,000 (1,000 to new contacts). Source: Outlook.com's own documentation, checked 6 Sep 2026 (page dated 2026-04-21).
What happens when you exceed the Outlook.com sending limit?
Sending blocked temporarily; repeated hits can suspend the account. Hitting the limit is also a reputation event: a mailbox that keeps running into it looks like a bulk sender to the provider's filters, so treat the limit as a ceiling you never approach rather than a target.
How many recipients per message does Outlook.com allow?
500.
How do I increase the Outlook.com sending limit?
new/free accounts get lower temporary quotas. Beyond the published caps there is no setting to raise them; the limit you hit first in practice is reputation, not the cap. A warmed mailbox that never approaches the hard limit sends more reliably than a fresh one that tests it.
Does the Outlook.com limit change how you warm up?
The 1,000 first-time-recipient cap is the one cold senders hit.