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The Risks of Bulk Emailing Through Microsoft 365

Ryan Bialek 2023-05-23

As businesses and organizations continue to rely on email as a primary means of communication, the need to send bulk emails has become increasingly common. However, sending bulk emails through Microsoft 365 and Exchange Online comes with inherent risks that need to be understood.

Risks associated with sending bulk emails through Microsoft 365 and Exchange Online (Outlook)

  1. Deliverability Issues: Whether for marketing or operational purposes like invoicing, when you plan on sending bulk emails, it's essential that the emails reach their intended recipients' inbox. Unfortunately, email services like Microsoft 365 (Exchange), Gmail, and others, have strict policies in place to prevent spam and other malicious emails from reaching inboxes. As a result, bulk emails sent through these services may be flagged as spam, and there's a high likelihood that they'll end up in the recipients' spam or junk folders.

  2. Reputation Damage: Sending too many emails or sending irrelevant content can damage your email reputation. When your emails are marked as spam, it negatively affects your organization's domain "sender reputation", which can lead to future emails being blocked or filtered out by services like Microsoft 365 and Gmail.

  3. Compliance Issues: When sending bulk emails, it's essential to ensure that you comply with all relevant laws and regulations, such as GDPR, CAN-SPAM, and CASL. Failure to comply with these regulations can result in significant legal and financial consequences.

Most importantly, bulk emailing through Microsoft 365 puts your entire organization's email communications and productivity at risk. Microsoft has established tenant-wide Sending limits and recipient rate limits on your email environment.

  • Generally, this is noted at 10,000 recipients per day (per mailbox). There are some exceptions and technical limitations. Whie this sounds like a lot of messages - bulk emailing through Microsoft 365 should still be discouraged.
  • Attempting to bypass this limitation by using Distribution Groups is not recommended.
  • Sending more than 30 email messages per minute will also result in throttling of excessive submissions at the user mailbox, and possibly system-wide.

Breaching Sending limits set by Microsoft can result in downtime for your mailbox as well as others in your organization. If you repeatedly exceed send limits, Microsoft may temporarily or permanently restrict your ability to send emails. This may also result in associated support and deployment costs.


Best Practices When Sending Bulk Emails Through Microsoft 365 and Exchange Online

To mitigate these risks, organizations should implement the following best practices when sending bulk emails through Microsoft 365 and Exchange Online:

  1. Use a Bulk Email Service Provider: Consider using an email service provider (ESP) that specializes in sending bulk emails. ESPs have dedicated servers and are designed to handle large volumes of emails while ensuring deliverability. Examples include Constant Contact, Mailchimp, and many more. Many of these services carry a subscription component - ensure you evaluate the service offering and provider reputation before settling for a free option.

  2. Invest in a CRM with email marketing capabilities, integration capabilities to third-party ESPs, or investigate custom integrations with a partner like Clear Concepts. Some common CRM platforms that include marketing capabilities are Dynamics 365, Hubspot, and Salesforce.

  3. Comply with Relevant Regulations: Ensure that you comply with all relevant laws and regulations governing email marketing, including GDPR, CAN-SPAM, and CASL.

  4. Use Email Authentication: Implement email authentication protocols such as SPF, DKIM, and DMARC to verify the authenticity of your emails and reduce the likelihood of them being flagged as spam. Clear Concepts can help your team run simple checks to determine if these protocols are in-use within your Microsoft environment.

  5. Contact Clear Concepts to enable Recipient Limits for your user mailboxes (1-1000). A value between 20-50 is a great way to prevent potential spam-like abuse from employees, whether intentional or not.

In conclusion, sending bulk emails through Microsoft 365 can be a fast way to communicate with large groups of people. However, it's essential to understand the risks involved and take steps to mitigate them. By following the best practices outlined above, you can increase the likelihood of your emails being delivered, improve your sender reputation, and reduce the risk of security incidents. Furthermore, giving your team the right tools can prevent organizational downtime.