For Microsoft 365 work or school mailboxes on Exchange Online, the recipient limit can be set up to 1000 people in one email, and the recipient rate limit is 10,000 recipients per day. You can also send 30 messages per minute. Microsoft says bulk newsletters should go through a third-party provider that specialises in them.
Exchange Online sending limits at a glance
Microsoft lists these on its Exchange Online limits page.
| Limit | Figure |
|---|---|
| Recipients in one message (To, Cc and Bcc together) | Customisable up to 1000 |
| Recipients per day | 10,000 |
| Messages per minute | 30 |
| Recipients on an encrypted message | About 200 |
| External recipients from a default onmicrosoft.com domain | 100 per organisation per 24 hours |
Checklist before a large Outlook send
Run through these before you press send on anything going to a long list. Each one maps to a limit Microsoft documents.
- Count every field. The per-message limit covers To, Cc and Bcc combined. Hiding people in Bcc doesn't free up room.
- Check what your admin has set. Recipient limits for existing mailboxes can be set anywhere between 1 and 1000, so your own ceiling may sit below the maximum.
- Look at how your list is stored. A distribution group kept in the organisation's shared address book counts as one recipient. A personal distribution list doesn't; each person in it counts separately.
- Add up the day, not just the message. The 10,000 daily figure counts recipients across everything the mailbox sends in a rolling 24 hours.
- Pace a run of messages. Sending more than 30 messages a minute goes over the message rate limit.
- Trim encrypted sends. If the message is encrypted, plan for a recipient limit of about 200.
- Check the sending domain. Outbound mail from default onmicrosoft.com domains is held to 100 external recipients per organisation within a 24-hour rolling window.
How groups and personal lists count towards the limit
Suppose you have the same group of colleagues saved two ways. As a distribution group in the shared address book, the whole group uses up a single recipient slot. Saved as your own personal list in Outlook, every member is counted one by one, so a large list can eat most of your per-message allowance on its own. If you're building lists for regular sends, our guide to group lists for business Outlook users is worth a read.
What happens once you hit the daily recipient cap
Reach 10,000 recipients and the mailbox stops sending. It doesn't reset at midnight. Messages can't go out again until the number of recipients you sent to in the past 24 hours drops back below the limit, so the wait depends on when your earlier sends went out. For anything time sensitive, that's the reason to spread a big send over more than one day.
Why Microsoft points newsletters elsewhere
Microsoft's own position is that customers sending legitimate bulk commercial email, newsletters included, should use third-party providers that specialise in that work. For a short internal update, see our Outlook newsletter walkthrough. For a large subscriber list, a dedicated sender is the route Microsoft recommends. If you also send from Gmail, its rules differ, and this guide to Gmail sending limits sets them out.
Frequently asked questions
Does Bcc get around the Outlook recipient cap?
No. Bcc addresses are counted together with To and Cc for the single message figure.
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Can my company lower the number of people I can email at once?
Yes. Admins can set existing mailboxes to any figure from 1 to 1000.
How many people can get one encrypted email?
Roughly 200, a far lower ceiling than the 1000 allowed on an ordinary message.
When can I send again after reaching 10,000 recipients?
When your rolling 24-hour total falls back under 10,000. There's no fixed reset time.
How many messages can I fire off in a minute?
30. Going faster runs into the message rate limit.
