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How to Fix the Exchange Online Mailbox Limit Exceeded Error
Question details
The user is encountering a Mailbox Limit Exceeded error when using an Outlook mailbox to send automated ticket responses and replies via Freshdesk.
- Product
- Exchange Online
- Device & OS
- not provided
- Scenario
- Sending a high volume of automated customer support ticket responses and notifications through Freshdesk using a standard Microsoft Exchange Online mailbox.
- Observed behavior
- The system throws a Mailbox Limit Exceeded error and blocks outgoing messages because the email volume has surpassed Exchange Online's hard-coded sending limits.
Verify your current Exchange Online sending limits and review your recent outgoing email logs to confirm exactly which limit (e.g., messages per minute or recipients per day) was triggered.
Switch to a High-Volume Email Provider
Exchange Online's standard sending limits cannot be increased. High-volume automated emails should be routed through dedicated transactional email services.
Microsoft Exchange Online enforces strict limits on messages per minute and recipients per day to protect its infrastructure from spam and abuse. Because these limits cannot be increased for standard mailboxes, expanding organizations must migrate high-volume tasks to dedicated mailing services.
Calculate the average and peak daily outbound emails sent by your Freshdesk system to determine your exact volume requirements.
Choose a high-volume email service designed explicitly for automated transactional emails, such as Azure Communication Services, SendGrid, or Mailgun.
Navigate to your Freshdesk email settings (Admin > Email) and replace the Outlook SMTP credentials with the API or SMTP server configuration provided by your new high-volume email service.
Configure Alternative Mail Routing in Freshdesk
Adjusting how Freshdesk handles outgoing messages can mitigate the issue by bypassing your custom Exchange server.
Boost Your Team's Productivity with WPS Office
While you resolve your Exchange Online and Freshdesk server configurations, ensure your team stays highly productive. WPS Office offers a lightweight, highly compatible alternative to Microsoft Office, perfect for managing your support metrics, reports, and internal documentation.
- 1. Download the installer: Visit the official WPS Office website and download the free installation package for your operating system.
- 2. Install WPS Office: Run the installer and follow the on-screen instructions to set up the software on your computer.
- 3. Open and edit your files: Launch WPS Office to immediately open, edit, and save your existing Microsoft Office documents without any formatting loss.
Frequently Asked Questions
What are the exact sending limits for an Exchange Online mailbox?
Standard Exchange Online mailboxes generally restrict sending to 30 messages per minute and 10,000 recipients per day. However, this can vary slightly based on your specific Microsoft 365 subscription tier.
Can I request Microsoft to increase my Exchange Online sending limits?
No, Microsoft strictly enforces these limits to protect their global infrastructure from spam and network abuse. They cannot be increased for standard user or shared mailboxes.
Why does Freshdesk trigger this error when manual sending works fine?
Automated systems like Freshdesk often send bursts of emails simultaneously (such as a batch of automated ticket receipts). This rapid output easily exceeds the strict 'messages per minute' threshold of Exchange Online, triggering the block.
