The specifications below outline message sending limits that apply to Colorado State and CSU Pueblo Microsoft 365 (M365) email accounts.
| Description | Limit |
|---|---|
| Maximum number of recipients in all emails sent in a 24-hour period | 2,000 recipients per 24-hours |
| Maximum number of recipients in all emails sent in a 24-hour period with granted exception* | 10,000 recipients per 24-hours |
| Maximum message size | 25 MB |
| Maximum attachment size | 35 MB |
| Maximum number of recipients in a single email | 500 recipients per email |
- These limits do not affect emails addressed to CSU distribution lists or mailing lists. Email sent to Exchange distribution lists are considered as being sent to a single recipient.
- Applied limits are subject to change by the Division of IT or if Microsoft modifies the service offering.
- Please refer to Microsoft 365: Exchange Online Limits for more information – settings applicable to CSU are categorized under “Microsoft 365 Enterprise E3/E5” or “Exchange Online Plan 2” sections of Microsoft documentation.
Frequently Asked Questions
Why are there sending limits?
When an account’s credentials are compromised, a bad actor can send mass email in an attempt to gain access to additional accounts. The Division of IT has set the default number of messages an account can send in any 24-hour period to 2,000 to limit the reach of a bad actor while also allowing a suitable range for the majority of CSU users to communicate effectively.
What happens if an account exceeds the daily limit?
The account will be blocked from sending additional email until the Division of IT is alerted, can confirm the account is not compromised, and administratively unblocks the account.
How is a day defined in this policy?
A day is defined as any rolling 24-hour period.
Is there an exception process?
If you have an M365 account (individual user or shared mailbox) that regularly sends large volumes of email where the 2,000 daily limit presents a problem, please submit a help ticket to help@colostate.edu and we will work with you to get an exception added.
You can also set up a mailing list that allows you to send messages to a list of subscribers.