I had a report of a user (Bob McUser) turning on their OOF but when people emailed them no auto response was sent. After some basic troubleshooting such as “is the OOF actually turned on?” it was time to dig deeper. Bob had over 100 rules so this is where I focused my attention as Exchange has a rule quota (default: 64KB), and ultimately OOF is a rule.

You can see what a users rules quota is set to using:

Get-Mailbox Bob.McUser | Select RulesQuota

64 KB (65,536 bytes)

Unfortunately there is no way to determine how much of the rules quota a user is using, but we can see how many rules they have. Keep in mind that the size of a rule is based on the name of the rule and it’s complexity – someone with 50 rules with long names that are super complex may fill their quota more quickly than someone with 200 rules that have short names and are simple – but at least this count is a good indication of a possible problem.

The following powershell will enumerate through all your users and count how many mailbox rules they have set-up (you could obviously filter it to only certain users, but I wanted to get an idea of how many rules most people had)

Get-Mailbox -resultsize unlimited | Add-Member ScriptProperty RuleCount {@(Get-InboxRule -mailbox $this.identity -erroraction silentlycontinue -warningaction silentlycontinue).count} -passthru | sort rulecount | select name, rulecountName

Name            RuleCount
----            ---------
Jess Wright            10
Alan Wood              16
Bob McUser            113

Bob didn’t have the most rules, but was definitely in the top 1-2%.

Luckily when a user sets their OOF and it fails, the mailbox server logs an error under event id 3004 with the message: The Rules quota of mailbox [email protected] has been reached and the automatic reply rules can’t be enabled or updated. Delete some existing rules or increase the user’s rule quota and try to set the automatic reply again. You can use the Set-Mailbox cmdlet to increase a user’s rules quota.

We can search all mailbox servers for this error, and return the users affected using:

Get-MailboxServer | %{ Get-WinEvent -FilterHashtable @{logname='application'; id=3004} -computername $_.name -erroraction silentlycontinue | select -expand properties | sort -unique }

[email protected]

Now we have definite proof of the issue, there are 2 options. Get the user to remove some rules, or expand their rules quota using the below powershell (256KB is the maximum allowed):

Set-Mailbox Bob.McUser -RulesQuota 256kb