[EXCH] Event ID: 9646 User exceeded the maximum of 500 objects of type “objtFolder”.

Shared mailboxes setup in cache mode will download entire content of the mailbox and will register every folder in each cached mailbox toward the objtFolder type limit on the server that’s running Exchange Server. By default, objtFolder limit is set to 500 per-mailbox limit.  Once the limit is exhausted, user will start experiencing the symptoms below:

– Inbox does not update automatically.
– Folder status bar shows “This folder was last updated on …” instead of “All folders are up to date” message displayed.
– Viewing items in secondary mailbox, new folders and items may not appear or seem to be missing.
– Deleted items still appear in the secondary mailbox like shadow items.
– Degraded performance or random hangs.

Exchange Server (Application log) – Error shows:
Event ID: 9646
Type: Error
Source: MSExchangeIS
Mapi session “/o=First Organization/ou=Administrative Group/cn=Recipients/cn=user”
exceeded the maximum of 500 objects of type “objtFolder”.

Solution 1: Disable Automap and seperate OST for caching (Preferred method)

1. Remove mailbox permissions
Remove-MailboxPermission -Identity <Mailbox ID1> -User <Mailbox ID2> -AccessRights FullAccess
2. Readd shared mailbox permissions without Automatpping
Add-MailboxPermission -Iden
tity <Mailbox ID1> -User <Mailbox ID2>-AccessRights FullAccess -AutoMapping:$false
3. Readd Mailbox from Mail item in Control Panel.
4.Select your profile, and then click Properties.
5.Click E-mail Accounts.
6.On the E-mail tab of the Account Settings dialog box, click New.
7.In the Choose Service section of the Add New Account dialog box, click E-mail Account, and then click Next.
8. Fill in the e-mail with the shard mailbox
9.Click Finish, click Close, click Close, and then click OK.
10.Start Outlook.

Solution 2: Disable caching of all shared folders (placing shared mailbox in Online Mode)

1.On the File tab, click Account Settings in the Account Settings list.
2.In the Account Settings dialog box, click the E-mail tab and then double-click your Microsoft Exchange Server account.
3.In the Change Account dialog box, click More Settings.
4.In the Microsoft Exchange dialog box, click the Advanced tab.
5.Click to clear the Download shared folders check box.
6.Click OK two times.
7.Click Next, click Finish, and then click Close.
8.Restart Outlook.

Solution 3: Increase the objtFolder count using Registry Key

. Open Registry Editor and navigate to:
2. Right click ParametersSystem and create New -> Key
3. Enter MaxObjsPerMapiSession and confirm creation of the new sub-key
4. Right click newly created key, create new DWORD value called objtFolder and give it a decimal value bigger than default 500.
5. Create another DWORD value called objtFolderView and give it the same value.


  • https://support.microsoft.com/en-us/help/3115602/performance-and-synchronization-problems-when-you-work-with-folders-in
  • https://support.microsoft.com/en-us/help/2646504/how-to-remove-automapping-for-a-shared-mailbox-in-office-365
  • https://exutils.blogspot.com/2011/06/exceeded-maximum-of-750-objects-of-type.html

Author Details
Contributer and Author Enterprise Communications Engineer Hi Epic

testest test 

0 0 votes
Article Rating
Notify of

Inline Feedbacks
View all comments