Outlook - Sending limits in outlook

Article Type: How To

Question: 

• What are the sending limits for emails in outlook?

Answer: 

In order to combat spam and phishing attacks, Microsoft has implemented sending limits. [https://docs.microsoft.com/en-us/office365/servicedescriptions/exchange-online-service-description/exchange-online-limits#receiving-and-sending-limits] At this time, Minnesota State has the ability to remove accounts from the blocked sender list, in coordination with campus IT security staff. Repeated violations of Microsoft's sending limits will require intervention from Microsoft.

• You are limited to 30 messages per minute.
  • The count is all activity in the account, so if you send 25 and answer another 5 you still hit the threshold. It is recommended that higher volumes of email sending be completed during off-hours/low activity time from a shared account.
  • When outbound message volumes surpass the message rate limit, any excess in message submission will be throttled and successively carried over to the following minutes. This will typically not block the sender's account, but Exchange Online isn't suited to accommodate bulk-mailing scenarios.
• Utilized a shared mailbox - (This may already exist. If not, we need to get one created. The shared mailbox should be used to send out mass messages.) The same rules apply to both individual and shared mailboxes, however, sending the message from a shared mailbox protects the individual's mailbox from inadvertently ending up on the block list when mass mailing is sent out. The individual mailbox would still be able to send/receive while the issue that flagged the shared mailbox is worked out.
• If you need to send to people internally we can help you set up a distribution list.
• Scheduled Mail Delivery - It may be best to schedule the delivery of messages in batches. [https://support.office.com/en-us/article/delay-or-schedule-sending-email-messages-026af69f-c287-490a-a72f-6c65793744ba] In order to stay clear of Microsoft's sending limits (mentioned above), it would be best to keep the list of recipients in each batch to less than 25, and schedule no more than one delivery per hour. This will allow other mail to continue to flow from the sending mailbox as expected.