MSExchangeIS Error 9646: ” Mapi session “/o=DOMAIN/ou=Administrative Group/cn=Recipients/cn=UserName” Exceeded the maximum of 500 objects of type “objtFolder” “

As the error message suggests, the user experiencing this error has more than 500 folder objects open. Although this sounds pretty strait forward – its extremely difficult to have over 500 folders open – and highly unlikely the user has done this on purpose!

In my case, three users were experiencing this issue and didn’t have any more than the usual Outlook window open.

There are two possible causes to check:

1. The user has some sort of third party search feature installed (such as Google Desktop). These third party applications will index the mailbox and cause a huge amount of connections to occur. Either remove the search agent or disable its indexing of the Outlook folders.

2. The user has “Download shared folders (excludes mail folders)” enabled in Outlook. This feature does a similar thing to Cached Exchange Mode however it is downloading a local copy of the shared mailboxes that the user may have open. Un-tick this box and the trouble should go away.