Reminders fire at 11:45 PM even though the sender did not include a reminder.

Reminder spam has been an ongoing problem for Exchange users. Reminder spam occurs when a user sends a meeting request with a reminder enabled. The organizer's reminder is set for the recipients rather than each recipient's own default reminder.

Exchange 2007 (and Exchange 2010) puts an end to "reminder spam" and overrides the sender's reminder, using the recipients default reminder settings. This works great, except for all day events without reminders. Exchange sets them to use the default appointment reminder, which many people leave at 15 minutes. Unfortunately for anyone who syncs their mailbox with a handheld device, the reminder on their device goes off at 11:45 PM.

Resolution

To resolve this issue in either Exchange 2007 or Exchange 2010, the Exchange administrator needs to create a config file on the Exchange server. Additionally, the administrator needs to install the latest update or rollup on Exchange server 2007.

Type or paste the following into NotePad and save the file as StoreDriver.config. It needs to be saved in the %ExchInstallFolder%\bin folder on the Exchange server.

The Transport service will need to be restarted and the administrator will need to add the config file to all Exchange servers that have the Hub Transport role.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
 <storeDriver>
  <parameters>
   <add key="AlwaysSetReminderONAppointment" value="false" />
  </parameters>
 </storeDriver>
</configuration>

A ready-to-use XML file is available at reminder-spam.xml.txt. Save the file and remove the .txt extension before dropping it in the bin folder.

Additionally, for Exchange 2010, the AlwaysSetReminderOnAppointment value is dependent on two Set-CalendarProcessing parameters that are configured for the receiving user’s mailbox:
AddNewRequestsTentatively (Default = True)
ProcessExternalMeetingMessages (Default = False)

These two settings must be set to True by running the following command:
Set-CalendarProcessing -AddNewRequestsTentatively:$True -ProcessExternalMeetingMessages:$True

In OWA, users can configure options to automatically place new meeting requests on the calendar, which are marked as Tentative and automatically process requests and responses from external senders.

If using Exchange 2007, the administrator needs to install at least Update Rollup 4 for Exchange Server 2007 Service Pack 1 on the Hub Transport server(s). However, I recommend installing the latest update for Exchange 2007. See How to Obtain the Latest Service Pack or Update Rollup for Exchange 2007.