After the update of McAfee Groupshield patch 701 on a Ms Exchange 2003 server we recieved the folowing error:

The exception information is:
System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.Exchange.Agents.AutoAccept.ConfigurationManager.get_Item(String key)
at Microsoft.Exchange.Agents.AutoAccept.EventSink.UpdateConfiguration(String sMailboxSMTP)
at Microsoft.Exchange.Agents.AutoAccept.EventSink.ProcessOnSaveEvent(String itemUrl DateTime& deliveryTime)
at Microsoft.Exchange.Agents.AutoAccept.EventSink.OnSave(IExStoreEventInfo pEventInfo String bstrURLItem Int32 lFlags)

from:

Event ID 4097
Source Auto Accept Agent

the SMTP temptables had to be manually purged in order to get emails going.

We took a closer look at mails that were queued and noted down the accounts that had emails in que .

We  recreated the mailboxes for those accounts. Also we restarted the SMTP service after resetting the que from registry

HKEY_LOCAL_MACHINESystemCurrentControlSetServicesSMTPSvcQueuing  РResetMessageStatus

(set it to 1).