LSUMail: Sending Limits

The Following Limits are Applied by Microsoft to your LSUMail Account

These limits are subject to change. For the most up to date information on these limits, see Office 365: Exchange Online Limits.


Maximum number of recipients in the TO, CC & BCC in a single e-mail:

500 recipients per e-mail

Maximum number of recipients in the TO, CC & BCC in all e-mails sent in a 24 hour period:

10,000 recipients per 24-hours

Maximum number of e-mails sent from your account per minute:

30 messages per minute

Maximum message size:

25 MB

Maximum attachment size:

35 MB

  • These Sending & Frequency Limits are high enough to not affect the average e-mail user.
  • The Limits DO NOT affect e-mails addressed to LSU Broadcast lists or to LISTSERV lists.  They also do not affect other mailing lists or groups hosted on the internet by Yahoo, Google, or Moodle.
  • Outlook or OWA Personal distribution lists; however, are affected because these lists are expanded to its membership when a messages is sent.

Why are there Sending Limits?

The limits were implemented to thwart massive spamming campaigns from e-mail accounts compromised by mass-mailing worms or viruses. 

If your LSUMail account gets compromised because you fell for a phishing scam or visited an infected web site, your e-mail account will probably be used to send massive amounts of spam.  This in turn will cause LSU to be blacklisted or blocklisted so that the e-mail system is no longer effective.

What Happens if you Exceed these Limits?

  • If you reach the 10,000 recipients per 24 hour limit, you will not be able to send any messages.  You will be able to receive messages.
  • You will have to wait 24 hours before you can send any new e-mails.
    • Note that the 24 hour period is a rolling 24 hour window.  Exactly when you can send a new message and how many recipients you can send to depends on your sending history in the previous 24 hours.
    • Waiting 24 hours does NOT clear you to send to another 10,000 recipients right away.  Once again it is a tally of how many recipients you previously sent to in the previous 24 hours that determines how many recipients you can send to at any point in time.
  • LSU cannot exempt from or fix any accounts that are in violation of these policies.

Best Practices

  • Departments and administrative units who use an LSUMail account to directly mass mail to a large number of recipients should meter their mail outs to fall below the Sending Limits. 
  • As an alternative, you can set up a listserv mailing list.


11/3/2022 8:29:36 AM