Office 365 Email Sending Limits: 2023 Guide

Written by

Michael Benson

Learn everything you need to know about Office 365's email sending limits. Navigate restrictions intelligently for seamless communication.

Outlook is one of the most widely used email client and service among individuals and businesses around the world. However, sending mass emails using Outlook has its limitations, which can impact your email campaigns if you are not familiar with their sending limits. Outlook also has certain restrictions that may be imposed on your account if you exceed their normal sending limits or your outgoing messages cause too many issues for recipients. Therefore, it is crucial to be aware of what Outlooks sending limits are and what activity may cause potential issues for their systems before commencing any active outreach campaign.

In this article, we will delve into what Outlooks sending limits per day are and provide you with the best practices to avoid restrictions and ensure the success of your email campaigns. Knowing the daily sending limit will assist in ensuring that all outgoing email campaigns run smoothly and achieve their intended objectives.

Understanding Outlook's Email Sending Limits

So what even are the standard limits placed under a Microsoft 365 environment for Outlook users, and why does Microsoft restrict these accounts to begin with? If you are paying for a service, you would think that it is up to you as the customer to determine how much activity you can perform, but Microsoft puts these limits under Microsoft 365 for good reasons, both for their own servers as well as your own.

Every email message that is delivered to a recipient's mailbox is logged and noted by the email provider themselves. These providers pay attention to the total amount of sending activity you are performing, the content of the messages you are sending out (message size, file sizes of attachments), as well as the email headers included in all outgoing messages. These providers primarily will keep track of this information in order to build up a profile on you as a sender in order to help combat spammers from performing email blasts that can be nefarious/detrimental to an unwilling recipient.

For the host email provider, they ideally want to stop potential spam from occurring or having 1 single user or workspace potentially causing issues for themselves by performing high amounts of sending activity in a short amount of time, so Microsoft 365 puts basic sending limits in place in for Outlook order to curve users sending habits.

Office 365 Email Sending Limits

For a standard Microsoft 365 environment, the following limits on sending activity are in place for Microsoft Outlook users.

- 10,000 email sends per day
- 500 recipients total per single emails end
- 30 email sends per limit

While these sending limits are very generous when compared to other popular email providers such as Google (Who limits all users to 2,000 email sends per day), it is important to note that these limits are in place to prevent spamming and maintain the overall health and performance of the email service. In addition, Microsoft offers options to increase these limits through their Exchange Online Protection service and Power Platform. It is recommended to check with your IT administrator or Microsoft support to ensure compliance with their sending policies and to explore options for increasing sending limits if needed for your business.

Tips for Staying Within Email Sending Limits

One of the most important things to keep in mind when working within email sending limits is to always focus on sending high-quality, targeted messages. By sending messages that are relevant and valuable to your recipients, you are more likely to see higher engagement rates, which can in turn boost your overall deliverability. As well, it is important to segment your email lists based on relevant factors like location, interests, and behaviors, and create personalized messages that resonate with each group, as this overall will help with the success of any outreach campaign or targeted advertising you plan on utilizing your workspace for.

Another key tip for staying within email sending limits is to avoid sending too many emails at once. While Office 365 and its associated services allow 30 messages to be sent per minute, you should never exceed or get close to this limit, as it can trigger automatic spam detection systems if your activity can be misinterpreted as malicious. Instead of blasting your entire list with a single message, consider breaking your sends up into smaller batches and sending them over a longer period of time. This can help you avoid triggering spam filters and ensure that your messages are being delivered to your recipients' inboxes, rather than their spam folders, as it should be the highest priority to ensure high deliverability rates to the primary inbox of your recipients to avoid wasting any initial contact with a potential client or customer.

When sending emails with larger files attached, it's important to be aware of your email provider's attachment size limit. Exceeding these limits can result in delivery failures or other issues, which can impact the overall success of your email campaign. In addition to checking your provider's attachment size limit, it's also important to consider the security implications of sending large files via email. In some cases, it may be more secure to use a file-sharing service or other alternative method for sending larger files, rather than attaching them directly to an email. By taking the time to carefully consider your attachment size and security needs, you can help ensure that your emails are delivered successfully and that your files remain secure.

Finally, it's important to monitor your email sending activity on an ongoing basis to ensure that you are staying within the limits set by your email provider. Most email marketing platforms offer built-in reporting tools that allow you to track your sending volume, engagement rates, and other important metrics. By keeping a close eye on these metrics and adjusting your sending strategy as needed, you can optimize your email campaigns for maximum deliverability and engagement. Additionally, make sure to regularly clean your email lists by removing inactive or invalid email addresses, as this can also help improve your deliverability rates.


What happens when the attachment size exceeds the limit set by Office 365?

When a file attachment exceeds the size limit set by your Office 365 workspace, the email will not be delivered and an SMTP 552 error message will be generated and returned back to the sender. The limit for attachments in Office 365 varies based on the subscription plan, but it typically ranges from 20 MB to 150 MB. If the attachment size exceeds the limit, you can try compressing the file or using a file sharing service such as OneDrive or SharePoint to share the file via a direct download link.

What should I do if I receive an error message when sending an email in Office 365?

If you receive an SMTP bounce back message when sending an email in Office 365, it's important to review the specific message to determine the issue. All errors regarding outgoing messages are returned with a specific SMTP code, with a given reason as to why this delivery failed. Depending on the error message, you may need to adjust your email settings or contact your email administrator for assistance.

Can I increase the allowable limit for sending emails in Office 365?

It is possible to increase the daily sending limit for outgoing emails in Office 365, but this will depend on the subscription plan. Generally unless there is a very specific reason as to why you need your daily sending limits increased, Microsoft tends to not make special exceptions for users. In general, it's important to be mindful of email size limits to ensure timely and successful delivery, as realistically it is better to maximize deliverability and maintain lower sending volumes than to maximize sending volumes with Office 365.

How can I reduce the file size of attachments to meet the maximum file size limit in Office 365?

To reduce the file size of attachments to meet the maximum file size limit in Office 365, you can try compressing the file or using a file sharing service such as OneDrive or SharePoint to share the file. Additionally, you may consider breaking up larger files into smaller segments or using a different file format.

Can I use multiple mail servers with Office 365?

It's not exactly possible to use multiple mail servers with Office 365, but as long as you have additional domains, you can setup multiple workspaces if you wish to split up sending volumes across addresses.

Can I use a different email account with Office 365?

You can use a different email account with Office 365 by adding the account to your workspace, but these can only be another outlook account. This can be useful if you have multiple email accounts or if you're using a shared computer. To add an email account to Office 365, simply navigate to the account settings and follow the prompts.

Can I track my emails to ensure they reach the intended recipient in Office 365?

Microsoft 365 does not directly offer tracking services for outgoing messages, but if you wish to track where your messages are being delivered you can utilize a pixel tracking service to get an idea on how your recipients are engaging with your messages. When the recipient opens or reads the email, you'll receive a notification confirming that the email was delivered or read. However, it's important to note that read receipts may not be reliable, as some email clients allow users to disable them. As well, any additional tracking services contained within an email message can run the risk of hurting deliverability, so keep this in mind as you plan your outreach campaign.


Outlook has sending limits that businesses need to know about to prevent being flagged for spam. Microsoft 365's email sending limits for Outlook include up to 10,000 email sends per day, 500 recipients per single email send, and 30 email sends per minute. However, sending high-quality, targeted messages and breaking up email sends into smaller batches can help avoid spam filters and ensure high deliverability rates. Monitoring your email sending activity and regularly cleaning your email lists can optimize your email campaigns for maximum deliverability and engagement.

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