YesterdayI started seeing these events in the Applicationlog:Event Type:WarningEvent Source:MSExchangeISEvent Category:General Event ID:8528Date:1/22/2009Time:9:51:30 AMUser:N/AComputer:EX01Description:The mailbox for /o=(removed for security reasons)/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=EX01/cn=Microsoft System Attendant has exceeded the maximum mailbox size. This mailbox cannot send or receive messages. Incoming messages to this mailbox are returned to sender. The mailbox owner should be notified about the condition of the mailbox as soon as possible. For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp. Event Type:ErrorEvent Source:MSExchangeIS Mailbox StoreEvent Category:Logons Event ID:1022Date:1/22/2009Time:9:51:30 AMUser:N/AComputer:EX01Description:Logon Failure on database "MSG1\MSG1-MS1" - Windows account MYFAMILY\MAIL03$; mailbox /o=(Removed for security reasons)/ou=Exchange Administrative Group (FYDIBOHF23SPDLT)/cn=Configuration/cn=Servers/cn=EX01/cn=Microsoft System Attendant.Error: 1245 Client Machine: MAIL03 Client Process: edgetransport.exe Client ProcessId: 0 Client ApplicationId: Client=Hub Transport For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.Data:0000: 76 74 f7 7d 24 b5 3e 4f vt}$>O0008: 9c 42 ee ab 37 60 4d 62 œB7`Mb0010: 5b 44 49 41 47 5f 43 54 [DIAG_CT0018: 58 5d 00 00 46 00 00 00 X]..F...0020: ff d8 21 00 00 00 00 00 !.....0028: 00 02 38 00 00 00 3a 67 ..8...:g0030: f0 1f fe 00 00 00 a4 1d .....0038: 40 10 0f 01 04 80 a4 19 @....€.0040: 40 10 0f 01 04 80 84 12 @....€„.0048: 40 10 05 00 07 80 59 16 @....€Y.0050: 40 10 dd 04 00 00 59 19 @....Y.0058: 40 10 dd 04 00 00 97 08 @....—.0060: 40 10 dd 04 00 00 @.... And if I do a get-mailboxstatistics on the "Microsoft System Attendant, I see this:AssociatedItemCount : 0DeletedItemCount : 0DisconnectDate :DisplayName : Microsoft System AttendantItemCount : 52192LastLoggedOnUserAccount : NT AUTHORITY\SYSTEMLastLogoffTime : 1/22/2009 10:05:24 AMLastLogonTime : 1/22/2009 10:05:24 AMLegacyDN : /O=(Removed)/OU=EXCHANGE ADMINISTRATIVE GROUP (FYDIBOHF23SP DLT)/CN=CONFIGURATION/CN=SERVERS/CN=EX01/CN=MICROSOFT SYSTEM ATTENDANTMailboxGuid : 7df77476-b524-4f3e-9c42-eeab37604d62ObjectClass : Mailbox, SystemAttendantMailboxStorageLimitStatus : MailboxDisabledTotalDeletedItemSize : 0BTotalItemSize : 102401746BDatabase : EX01\MSG1\MSG1-MS1ServerName : EX01StorageGroupName : MSG1DatabaseName : MSG1-MS1Identity : 7df77476-b524-4f3e-9c42-eeab37604d62IsValid : TrueOriginatingServer : ex01.(removed)I The TotalItemSize is no where close to the 500 MB limit on the mail store. The StorageLimitStatus changes to BelowLimit, but then it changes back. The ItemCount has grown to 52200 before, but always has a MailboxDisabled if it goes above 52200Any suggestions? I have also tried to find detailed info on what exactly is in the "Microsoft System Attendant" mailbox but have not had much succcess.Any help or guidance would be appreciated.

Hi Mike,- You can check below article to understand what is system attendant mailbox and various FAQs about it. This article is for 2000/2003 but SA mailbox is same for Exchange 2007 also.Overview of Exchange 2000 Server and Exchange Server 2003 Special Mailboxeshttp://technet.microsoft.com/en-us/library/aa996235(EXCHG.65).aspx- SA mailbox doesn't follow limit of mail store (which is 500MB in your case), ithas it's own custom mailbox size limit and you can increase it by modifying an AD attribute through ADSIEdit.msc because ultimately all settings are stored into AD of course :)- Check the properties of System Attendant mailbox in ADSIEdit.msc (adsiedit.msc is a part of support tools), path is below...CN=Microsoft System Attendant,CN=<sservername,CN=Servers,CN=<Exchange 2007 Admin Group Name>,CN=Administrative Groups,CN=<orgname>,CN=Microsoft Exchange,CN=Services,CN=Configuration,CN=<domain>Find an attribute named mDBOverHardQuotaLimit. It should have by default value 100000, modify it to 200000 to increase the mailbox size limit of System Attendant mailbox.- Normally SA mailbox doesn't receive mails but if this happens again and mailbox size reaches to 200MB then you need to find out why it is being filled up.Amit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com

Amit, thanks for the reponse. The information was very informative. I have made the change in ASDIEdit, but I am still getting the status of the mailbox as MailboxDisabled. I have restarted the Microsoft System Attendant service and dismounted and remounted the database with the System Attendant mailbox in it.Do you have any other suggestions?

I must not of given enough time for replication or something, but it looks like it has worked now. thanks for the solution.

Kewl, it is Information Store service which you needed to restart for immediate effect :)Mailbox Size Limits Are Not Enforced in a Reasonable Period of Timehttp://technet.microsoft.com/en-us/library/bb684892.aspxAmit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com

I am now facing the similar problem and I have question want to ask.1. How can I login the System Attendant mailbox to clean up the mail?

did your question ever get answered, BlutPluto? I need to do the same...