• 100 GB mailbox quotas for users
• 50 GB mailbox quotas for unified groups

Office 365 Limits

Office 365 limits

Maximum number of messages per mailbox folder	1 million
Maximum number of messages per folder in the Recoverable Items folder	3 million
Storage quota for Recoverable Items folder	100GB
Maximum number of subfolders per mailbox	10,000
Maximum folder hierarchy depth	300
Message size limit	100 MB
Subject length limit	255 characters
File attachments per message limit	250
Messages received	3,600 per hour
Recipient rate limit	10,000 recipients per day and up to 1000 an hour for Employee
Recipient rate limit (Resource Accounts and 2FA enabled Users)	1,000 recipients per day and up to 500 an hour
Recipient rate limit (Non-2FA enabled Users)	100 recipients per day and up to 50 an hour
Recipient limit	500 per message
Message rate limit (SMTP client submission only)	30 messages per minute
Maximum number of distribution group members	50,000
Maximum message size for large distribution groups (>5,000 members)	2 MB
Exchange ActiveSync device limit	100
Exchange ActiveSync file attachment limit	25 MB
smtp.office365.com max concurrent connections per mailbox limit	3
Junk Email folder retention period	30 days

 

Exchange Recipient Limits 

Depending on your affiliation with the University, you will fall into one of the four policy groups designed to protect your exchange mailbox.

How do I know I've been blocked?

When someone has exceeded their sending recipient limit, they will get a system generated message. The messages will contain the following error code:

"Remote Server returned '550 5.1.8 Access denied, bad outbound sender AS(42004)'"

How many emails can I send per day/hour?

Based on your affiliation and if you are challenged for 2-factor authentication, you will have different limits.

Type of Email Account and allowed email recipients
Type of Email Account	Challenged in Duo 2FA (MFA)?	Allowable number of Recipients
Employee	Yes	10,000 email recipients a day and up to 1,000 an hour
Resource Accounts	Not Applicable	1,000 email recipients a day and up to 500 an hour
Undergrad/Graduate Student, Retiree, Affiliate	Yes	1,000 email recipients a day and up to 500 an hour
Undergrad/Graduate Student, Retiree, Affiliate	No	200 email recipients a day and up to 100 an hour

If you are an undergraduate who is enrolled in Duo but not challenged for MFA on Office 365, but have a business need to send above the lowest limit; you will need to fill out an exception request by following the link https://go.illinois.edu/email-rate-exception.

How do I get unblocked?

Unfortunately there is not an override for these types of blocks as they come from Microsoft. Your daily count will reset at 7pm each day, so you will need to wait until this time to send emails again.

How do I avoid getting blocked again?

If you do not have MFA enabled, you can enroll by selecting the option that works for your situation.

• Use a bulk email service like Email+ part of the Public Affairs Webtools or University Housing's StarRez Portal. For information on these  and other options, please see: Email, Guidelines and best practices for sending bulk mail
• If you are an undergraduate who is enrolled in Duo but not challenged for MFA on Office 365, but have a business need to send above the lowest limit; you will need to fill out an exception request by following the link https://go.illinois.edu/email-rate-exception.

 

Your Outlook Email And Calendar Storage Size 

Mailboxes for Users on the Exchange system have a hard limit of 100GB

Current Warnings:

• 98GB: Warning regarding Inbox Size
• 99GB: Unable to Send Email
• 100GB: Unable to Send and Receive Email

Users may also experience performance issues when exceeding the following thresholds:

Total Mailbox Items: 250,000
Total Calendar Items: 5,000

Large numbers of recurring meetings, or long-lived recurring meetings can also have an adverse effect on performance.

**In the Windows Outlook desktop client, the item count in each Mailbox folder will show at the bottom left corner.**

There are several ways to reduce your mailbox size. You can make an offline backup as you prepare to delete emails.

Please note regarding backing up email, that you will need to keep track of the backup file or you will lose your backup archived information. You are responsible for storing and maintaining the backup file. In addition, you are responsible for importing that backed-up data into your mailbox if needed later. Anything that gets moved or deleted is due to your actions and no automated systems are in place to manage that data for you.

https://support.microsoft.com/en-us/office/back-up-your-email-e5845b0b-1aeb-424f-924c-aa1c33b18833

Export items to an archive file in Outlook for Mac - Microsoft Support

After making this backup file, you can delete the specified items from your inbox and then delete the items from the Recovery folder to complete the process of saving space.

To also save space, you can delete old items that are no longer wanted. Further examples of how to do this are below.

Please note that you remain solely responsible for emails or mailbox items that are deleted and permanently removed. Emptying the Deleted items folder puts the emails into the Recovery folder. Then you must also empty the Recovery folder to save space. At this point, you will not be able to recover items deleted from the Recovery folder. Please verify that you do not want the deleted email before you remove it, because these mailbox items once deleted and emptied from your recovery folder cannot be recovered and are permanently deleted.

Empty the Junk Email folder – Periodically empty the Junk Email folder to save your inbox space for messages you actually want.

Store attachments outside your mailbox – As attachments accumulate over time, they can take up a lot of space. For attachments you want to keep, consider saving them to a team site, to OneDrive, or to folders on your computer.

How to clean up your Mailbox via Outlook on the web:

Clean up Mailbox in Outlook on the web

Other ways to reduce your storage with Outlook on the web:

Organize your inbox with Archive, Sweep, and other tools in Outlook on the web - Microsoft Support

How to clean up your Mailbox via the Windows Outlook (Classic) desktop client:

You can use the Mailbox Cleanup tool to view the size of your mailbox and individual folders. This tool can also help you search for older or very large messages that you might want to delete.

Often, the cause of a large mailbox is a large Deleted Items folder. The tool provides a button to view the size of your Deleted Items folder and empty your Deleted Items folder.

Run the Mailbox Cleanup tool

Click the File tab > click Tools > Mailbox Cleanup
For a full rundown of this tool and its capabilities click here.

Another way to reduce your Calendar size:

Click the Calendar icon > click View tab > click Change View > click List

Select "View" from the top menu bar, click "Arrange by" and choose "Start Date." At this point, you can clean up as needed.  Make sure to check the ending date before deleting any recurring appointments. Deleting one instance of a recurring event will also remove all future appointments related to that event.

How to clean up your Mailbox via Outlook for Mac:

Clean up old email on Outlook for Mac - Microsoft Community

Archive Email in Outlook for Mac

Current instructions for Mac Archive can be found here.