These limits are high, so it is unlikely that an “average” user is going to come anywhere close to getting throttled. What can I do about mailboxes getting close to or hitting the limits? If you see a mailbox on this report that is getting close to the limits outlined above, it might be time to take some corrective action.
#EMAIL THROTTLED MEANING HOW TO#
I’m not going to go into how to get this information directly from the Graph, but that information is out there for those of you interested.įor our purposes here, I think this report is going to get most of you the information you need. If you want to get this data reported in real-time, you are going to need to dive into the Graph. As I am writing this, it is March 11 (2021), so this is not real time data. Go to Reports > Usage > Exchange and you will see a report like this:Īs you can see, I sent 50 messages and received 1,612 with the last activity date of March 9 (2021). This information is available in the “reports” section of the Microsoft 365 Admin center. How do I know if any of my mailboxes are close to those limits? The user will not be able to send messages again until 09:00 AM the next day. For example, a user sends an email message to 5000 recipients at 09:00 AM, then sends another message to 2500 recipients at 10:00 AM, and then sends another message to 2500 recipients at 11:00 AM, hitting the limit of 10,000 messages. The timer here is a 24-hour counter, meaning you can not send messages to 10,001 recipients within any 24-hour period. Each recipient in a personal distribution list count separately. It is important to note that a message sent to a distribution group stored in the tenant’s shared address book counts as 1 no matter how many recipients are in that DG.
Sending Rate Limit - ExO mailboxes have a limit of 10,000 messages per 24 hours sent to individual recipients. The change here is that this limit is now being enforced.
Receiving Limit - For all Exchange Online mailboxes, regardless of license, the receiving limit is 3,600 messages per hour as stated above. I will try to explain the limits I see being most relevant to customers below. Microsoft does have a page describing many of the limits applied to Exchange Online, but it is not super clear and I do see some holes in that document. It is entirely possible that you could have different limits on different mailboxes within the same Exchange Online tenant.
#EMAIL THROTTLED MEANING LICENSE#
There are quite a few different limits for Exchange Online mailboxes, and those limits do vary somewhat based on the license for each mailbox. Oh, what a fun question to try to answer. What are the rate limits for Exchange Online? The counter will reset one hour after the throttling starts, at which point the mailbox will go back to functioning normally. When a mailbox reaches this limit, any messages sent to that address for the next hour will be rejected with an NDR and the mailbox will receive a notification that it is being throttled. However, these limits also apply to Groups and to Public Folders so some organizations may run into that limit for theses mailboxes. If I got that many messages in my inbox, I am pretty sure I would be thinking about options for a career change.
I would think for most user mailboxes, 3,600 messages per hour received is enough. The change is that this preexisting limit will now be strictly enforced by Microsoft where it had not been enforced in the past. In their recent Exchange Team blog post " Upcoming changes to mailbox receiving limits: Hot Recipients Throttling", Microsoft announced that they are starting to enforce the already in place mailbox receiving limit of 3,600 messages per hour.
I thought this would be a good time to go though the limits that are in place for your Exchange Online mailboxes, and what you can do if you find yourself in a situation where those limits are negatively impacting your organization. Microsoft is currently in the process of enforcing some of these limits that have not previously been enforced. However, I find that few Exchange Online administrators know exactly what those limits are, how they work, why they are there, or what you can do about them. We all know there is a limit to how many emails you can send and receive, how much storage you can use, how much data you can move into or out of Exchange Online, and how big each individual email can be. I expect we all know there are limits to what you can and cannot do with your Exchange Online mailbox.