Outlook Email Sending Limits: How Many Can You Send?

TL;DR (Microsoft’s documented defaults, verified July 2026)

Microsoft 365 work and school accounts (Exchange Online): up to 10,000 recipients in any 24-hour period, 500 recipients per single message by default (admins can raise it to 1,000), and no more than 30 messages per minute.
Personal Outlook.com accounts: up to 5,000 recipients per day for Microsoft 365 subscribers, of which no more than 1,000 a day can be people you have never emailed before. Free and new accounts get lower limits.
These are Microsoft’s limits, not Outlook settings. You cannot raise them yourself, but your admin can adjust some of them.

You are about to send a big batch of emails from Outlook. How many is too many?

Here are the numbers that matter, what actually happens when you cross them, what Outlook and Word can do on their own, and how to run large sends without ever getting close.

The limits at a glance

Account type	Recipients per day	Recipients per message	Message size
Microsoft 365 work / school (Exchange Online)	10,000 (in any 24-hour period)	500 default, up to 1,000 if raised by admin	35 MB default, up to 150 MB if raised by admin
Outlook.com with a Microsoft 365 subscription	5,000 (no more than 1,000 to people you have never emailed)	500	25 MB per attachment (larger files can be shared as OneDrive links)
Outlook.com free account	Lower and variable; new accounts most restricted	Lower, Microsoft does not publish a number	25 MB per attachment (larger files can be shared as OneDrive links)

A few important details:

The daily limit counts recipients, not messages. One email to 500 people uses 500 of your 10,000, and so does 500 individual emails to one person each.
Exchange Online (the email service behind Microsoft 365 work and school accounts) also limits how fast you can send, to 30 messages per minute. Anything faster is slowed down and carried over to the next minute, not bounced.
Organizations also have a limit on outside recipients for the whole company that caps how many people outside the organization everyone together can email per day. It depends on how many licenses the organization has.
Your organization can set lower limits than these defaults. Trial tenants (a trial Microsoft 365 setup) can email at most 5,000 outside recipients a day, and addresses ending in onmicrosoft.com only 100. If your numbers look smaller, ask your IT administrator.
The limits exist to stop bulk and spam email from overloading Microsoft’s service, which also protects how well your normal email gets delivered.

What happens if you exceed the limits?

The symptoms differ by which limit you hit:

Sending faster than 30 messages per minute: nothing breaks. Exchange slows you down and the extra messages wait their turn.
Exceeding the daily recipient quota: Microsoft rejects the message with a notice such as “The message can’t be submitted because the sender’s submission quota was exceeded” (it may appear with a code like 554 5.2.0). Microsoft’s own advice is to wait one day. Messages may also sit in the Outbox until enough time has passed.
Suspicious sending patterns: separate from the quotas, Microsoft can block traffic it considers abusive (see why a mail merge bounces for what each error means and how to recover). A mailbox blocked for this reason usually stays unable to send until your administrator releases it.

The daily quota covers any 24-hour period rather than a calendar day, so a blocked send usually recovers on its own within a day. A mailbox that is blocked for suspicious sending is much harder to restore, so the goal is never to hit the wall in the first place.

What Outlook, Word and Microsoft 365 can do on their own

Before adding any tool, it helps to know what you already have:

Plan around the limits. A mail merge to 2,000 rows counts as 2,000 recipients, because each recipient gets their own email. See how to send a mass email in Outlook for the basics.
Split a large list by hand. Send part of the list today and the rest on later days, keeping each day under your quota.
Delay a single message. Outlook can hold one message and send it later. A rule can also defer delivery of outgoing messages, by up to 120 minutes.
Merge from Word. Word’s mail merge can send email through Outlook for Mac and the desktop version of Outlook on Windows. The new Outlook and Outlook on the web have no Word email merge.
Ask your administrator. Your Microsoft 365 administrator can raise the per-message recipient limit to 1,000 and the message size limit. Very high volumes are what dedicated bulk services or Azure Communication Services are for.

Why Outlook alone cannot pace a large send

Outlook has no daily cap and no built-in delay between the messages of a batch. A rule can only defer delivery by up to 120 minutes, which is far too short to spread a large send over several days. So if you send a big list in one go, you either blast through your quota or you split and send it by hand, day after day.

That is the gap SecureMailMerge fills. It sends through your own Microsoft 365 mailbox, so messages come from your normal address, and it lets you set a daily cap, a delay and sending hours for each campaign. Microsoft’s limits stay exactly as they are; the add-in helps keep your send inside them.

Pacing a mail merge with SecureMailMerge

One point to know first: the add-in’s daily cap counts messages per calendar day, while Microsoft counts recipients over any 24-hour period, and CC and BCC recipients add to Microsoft’s count. Leave yourself some room below your quota.

Step 1: Open the advanced options

In the campaign manager, select the link that shows or changes advanced options. See the advanced options reference for the whole screen.

Step 2: Set a daily limit

Tick “Limit how many are sent each day” and choose a number. Anything over the cap automatically moves to the next sending day, so a very large list is spread over several days without any manual splitting.

Step 3: Add a delay between messages

In the “Schedule” group, set a delay between messages so your send trickles out instead of arriving in one burst.

Step 4: Choose sending days and hours

Restrict sending to specific weekdays and a time window, for example business mornings only. See mail merge campaign limits for product specifics.

Frequently asked questions

How many emails can I send at once in Outlook?

A single email can go to 500 recipients by default on Microsoft 365 work and school plans (up to 1,000 if your admin raises it). In any 24-hour period, the ceiling is 10,000 recipients. Personal Outlook.com accounts with a Microsoft 365 subscription get up to 5,000 recipients per day, and no more than 1,000 a day can be people you have never emailed before. Free accounts get lower limits.

How many emails can I send per day with a mail merge?

On Microsoft 365 work and school accounts the 10,000 daily quota applies, and your organization’s limit for outside recipients may be lower. A mail merge to 1,000 rows counts as 1,000 recipients. Use a daily cap and sending delay to pace larger campaigns.

Can I increase my Outlook sending limit?

Not as a user. Some limits (like message size) can be raised by your Microsoft 365 administrator, and higher-volume needs are what dedicated bulk services or Azure Communication Services are for. For typical mail merge volumes, staying under the standard limits with pacing is enough.

Why is my limit lower than 10,000?

Trial Microsoft 365 setups can email at most 5,000 outside recipients a day, and addresses ending in onmicrosoft.com only 100. Administrators can also configure stricter limits. Check with your IT team; Microsoft’s published numbers are defaults, not guarantees.

What happens if I exceed the Outlook sending limit?

Microsoft rejects messages with a notice that the sender’s submission quota was exceeded, or they sit in the Outbox. Microsoft’s advice is to wait one day. Repeated suspicious sending can block the mailbox from sending until your administrator releases it.