Office 365, Exchange Online Protection, 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

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.


KeywordsExchange Online Protection 5.1.90 5.1.8 daily limit exceeded email limit too many emails send sending recipients recipient limits recipients exceed can't block blocked   Doc ID118081
OwnerOffice 3.GroupUniversity of Illinois Technology Services
Created2022-04-20 13:48:15Updated2022-10-18 16:13:08
SitesUniversity of Illinois Technology Services
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