If you’ve ever wondered, “How many emails can I send at once in Outlook?” you’re not alone. Microsoft Outlook—whether you’re using a free Outlook.com email account, a personal Microsoft 365 subscription, or a business Exchange Online mailbox—has strict sending limits in place to protect both senders and recipients.
These limits cap the number of messages, recipients, and even the size of attachments you can send in a single go. In this guide, we’ll break down exactly what you need to know about Outlook’s email sending limits in 2026, helping you stay within the rules while maximizing your productivity.
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Understanding Outlook’s Email Sending Limits
Default Sending Limits for Outlook
Outlook has built-in limits to ensure the system remains secure and free from spam. If you’re a Microsoft 365 subscriber, you can send emails to up to 5,000 recipients per day, but only up to 500 recipients in a single message. For free Outlook.com users, the limits are lower, typically around 300 recipients daily. However, this number may vary depending on your account’s age and reputation.
Outlook also differentiates between “relationship” recipients—those you’ve emailed before—and “non-relationship” recipients. For the latter, there’s a stricter limit of 1,000 recipients daily to prevent misuse. Additionally, for corporate Exchange Online accounts, the message size limit is typically 10 MB per email, whereas Outlook.com allows attachment sizes up to 25 MB.
Factors Influencing Sending Limits
Several factors can influence your sending limits beyond just the type of account you have. For instance, Microsoft may apply temporary lower quotas for new accounts as they build credibility within the system.
Usage patterns and history also play a significant role. Frequent bulk mailing can trigger throttling or even blocks. Starting in 2025, Microsoft plans to introduce a tenant-wide outbound external email limit for organizations using Microsoft 365. This will cap the total number of external emails sent by all users within a tenant over a rolling 24-hour period.
The limit will depend on the number of Exchange Online licenses your organization holds. Larger license counts may result in lower average limits per user, potentially affecting workflows like sales and marketing.
Other factors, such as physical mailbox storage limits, address book capacities, and specific mailbox policies, can also impact your sending capacity. For instance, Exchange Online typically sets an address book limit of around 1,000 entries for most business plans.
If you exceed these sending limits or message size restrictions, you might encounter Non-Delivery Reports (NDRs) or temporary blocks. These limits generally reset after 24 hours or at midnight based on the system’s timezone.
How Outlook’s Sending Limits Impact Users
Impact on Personal Users
For personal users, Outlook’s sending limits can sometimes feel restrictive, particularly if you often email large groups of friends, family, or club members. Free Outlook.com accounts generally allow sending emails to approximately 300 recipients per day. While this limit is sufficient for everyday communication, it may pose challenges for mass emails, such as invitations or newsletters. If you attempt to send an email to more than 500 recipients at once—the maximum allowed per message—you’ll need to divide your contacts into smaller groups.
Exceeding these limits can result in temporary sending blocks or Non-Delivery Reports (NDRs), which could delay your communication. Additionally, the attachment size limit of 25 MB per email means you might need to use OneDrive for sharing larger files, helping you avoid bounce backs and ensure smooth delivery.
Impact on Business and Professional Communications
Businesses and professionals using Outlook and Exchange Online must respect sending limits. For many Microsoft 365 users the default is a maximum of 500 recipients per message and, in some consumer/business subscriber cases, up to 5,000 recipients per day.
On the enterprise side, the tenant-wide outbound limits (especially for external recipients) become more significant: Microsoft has announced a formula-based limit tied to number of licenses (TERRL) and phased enforcement beginning in 2025-26. Exceeding these limits (e.g., in large marketing campaigns or mass notifications) may result in temporary throttling, delivery delays or blocked messages. To overcome these challenges, many businesses are turning to strategies like distribution groups, segmentation, or integrating third-party email marketing tools with Outlook to ensure compliance with sending limits while maintaining efficiency.
Business accounts also face stricter attachment size limits—typically 10 MB. Utilizing cloud services such as OneDrive or SharePoint becomes essential for sharing larger files. Failure to manage sending rates and file sizes effectively can activate spam filters or cause delivery failures, potentially harming professional reputation and communication productivity.
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Best Practices for Effective Email Management
To stay within Outlook’s sending limits and maintain smooth communication, it’s important to adopt smart email practices. Start by segmenting your recipient lists. Sending smaller batches of emails throughout the day, rather than one massive blast, helps you avoid hitting daily or hourly caps. This strategy also enhances deliverability since sudden spikes in email sending can trigger spam filters or result in temporary blocks.
Regularly clean your contact lists to remove outdated or inactive addresses. This not only ensures compliance but also boosts engagement rates. When sending large files, use cloud sharing links instead of attachments to stay within the attachment size limit and prevent delivery failures.
Additionally, monitor your mailbox size and folder organization. Regularly archiving old messages frees up storage space and keeps Outlook running efficiently.
Using Outlook Tools and Add-ons
Outlook provides several built-in tools to help manage your email workflow while staying within limits. The Focused Inbox feature, powered by advanced machine learning, automatically separates high-priority messages from routine updates, enabling you to focus on what requires immediate attention.
Rule-based folders allow you to automate the sorting of incoming emails by sender, subject, or keywords, making it easier to handle large volumes of messages. For those who need to send emails at specific times, scheduling emails is an excellent way to spread out your sending and avoid rate limits. Outlook also supports integrations with third-party add-ons and platforms, which can assist with bulk sending, analytics, and deliverability monitoring.
By utilizing these tools, you can maximize productivity while ensuring compliance with Outlook’s sending policies.
Conclusion
Understanding Outlook’s email sending limits is essential for maintaining smooth communication—whether you’re a personal user or managing large-scale business campaigns. Keep in mind that free Outlook accounts limit you to 100 recipients per message and 300 recipients per day, whereas Microsoft 365 allows up to 500 recipients per message and 10,000 recipients per day for bulk emails.
Other factors such as attachment sizes, message rates, and mailbox storage limits can also impact how effectively you send emails. To avoid disruptions, take proactive steps: segment your recipient lists, use cloud-sharing options for large files, and take advantage of Outlook’s scheduling and organizational tools.
If your email requirements surpass these limits, consult your IT administrator or consider using integrated email marketing platforms to scale your operations safely and efficiently.
FAQ
What are the daily email sending limits for Outlook.com and Microsoft 365 accounts in 2025?
In 2025, Outlook.com’s free accounts have a daily sending limit of approximately 300 recipients, with a maximum of 100 recipients per message. On the other hand, Microsoft 365 accounts allow sending up to 10,000 recipients per day, with a limit of 1,000 recipients per email.
Additionally, new external recipient limits for Microsoft 365 were introduced in 2025, capping at 2,000 external recipients daily. These limits are rolled out in phases depending on the number of licenses owned. For large organizations, limits scale with the number of licenses, enabling the possibility of sending tens of thousands of emails per day.
How does Microsoft determine the maximum number of recipients allowed per email in Outlook?
Microsoft calculates Outlook’s maximum email recipient limits based on subscription type and anti-spam policies, ensuring optimal server performance. Typical limits include 500 recipients per message and daily limits ranging from 5,000 to 10,000 recipients for Microsoft 365 subscribers. These limits may vary depending on factors such as account age and usage history.
Are there any new tenant-wide limits on external email sending for Microsoft 365 organizations, and how are these calculated?
Microsoft 365 introduced a new tenant-wide external email sending limit known as the Tenant External Recipient Rate Limit (TERRL), effective from May 1, 2025. This limit restricts the total number of external recipients a tenant can email within a rolling 24-hour period. The calculation formula is:
500 × (licenses^0.7) + 9,500
This formula varies depending on the number of Exchange Online licenses owned. If the limit is exceeded, further emails to external recipients will be blocked.
What should I do if I reach my Outlook email sending limit and my messages aren’t being delivered?
If you reach your Outlook email sending limit, wait for 24 hours for the limits to reset. Afterward, try reducing the number of recipients per email or split your mailing list into smaller groups. Consider upgrading to Microsoft 365 for higher limits or using third-party email services.
To prevent future blocks, avoid rapid bulk sending. Admins can manage or disable alerts through the Microsoft 365 Defender portal.