Microsoft Office 365 - Email - Sending Limits FAQs

Frequently Asked Questions (FAQs)

Table of Contents

• What are the sending limits and affected groups?
• Why are these limits in place?
• What happens if I exceed one of the limits?
• What should I do if my account is restricted due to exceeding one of the limits? 
• Will I receive an error message if I break the limit?
• What if I regularly need to send mass emails?
• What if I still need an exception to the sending limits?

Questions & Answers

What are the sending limits and affected groups?

• Students who have applied, or are admitted but not enrolled.
  • 50 internal recipients per hour. 
  • 50 external recipients per hour. 
  • 500 recipients per day.
• Students, alumni, and retirees without an employee role. 
  • 250 internal recipients per hour. 
  • 250 external recipients per hour. 
  • 600 recipients per day.
• Current Employees and Mail Enabled Service accounts for all campuses.
  • 10,000 recipients per day, for more details see sending limits found here: https://learn.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#sending-limits-1

Why are these limits in place?  

• The limits will reduce the impact and spread of credential harvesting and phishing attacks. 

What happens if I exceed one of the limits?

• If an individual sends an email that would put them over one of their limits, the email will fail to deliver to all recipients.  
• Their account would be restricted from sending mail until reviewed by an Administrator.  
• An alert will be sent to IT Security to review. 
• Logins for your account may be blocked if the sent emails are deemed malicious.

What should I do if my account is restricted due to exceeding one of the limits? 

• You can contact the Helpdesk at helpdesk@okstate.edu or 405-744-4357. 
• If logins for your account are blocked, you may receive further instructions for account recovery. 

Will I receive an error message if I break the limit?

• An email delivery failure notice will be sent to the sender for each email they send after being restricted.
• It will list all email addresses for which email delivery was blocked.
• The error reason will be “Sending email address not recognized as a valid sender” or “550 5.1.8 Access denied, bad outbound sender.” 

What if I regularly need to send mass emails?

There are a few options available that can be requested by a sponsoring department’s ITC. 

• Mail-enabled service accounts.
  • A separate mailbox that can be used to send mail.
  • Documentation: https://it.okstate.edu/services/service-accounts/index.html
• Exchange Email Distribution lists
  • Can be populated automatically based on department or other information.
  • Limited to internal recipients only.
• Listserv mailing list.
  • The recipient list must be manually updated.
  • These lists can include internal or external recipients.
  • Documentation: https://it.okstate.edu/services/email-lists/

What if I still need an exception to the sending limits?

• We cannot make an exception for the 10,000 recipients per day limit. 
• An exception will need to be sponsored by a department’s ITC.