Meetings with external organizer taking too long to appear on calendar


In a strange scenario, a manager’s secretary constantly said that the appointments/meetings updated or canceled by external organizers were taking too long to appear on his calendar. She reported that it often took hours or even days. This happened, for example, with updates of meeting location or cancellations.


The first step was figuring out if this could be an Outlook problem. We changed the Outlook setting from cache mode to online mode, but the problem persisted, either in OWA.

The second troubleshooting was at the SMTP level. You may be wondering, but why SMTP level? Because although appointments are not properly emails, they are sent as an email by using the SMTP protocol. After an invite arrives in the user’s mailbox, Exchange sees that message contains attributes which differs it from a normal email. Then converts it into an appointment. In the case of meetings that already had their approved invite, when the organizer makes any changes, the message should arrive in the recipient’s inbox, and Exchange Server should quickly convert the message into an appointment and delete from inbox.

I made some tests with Message Tracking for comparing the time which a cancellation sent by the organizer. In fact, I realize that it wasn’t an SMTP issue because the “cancellation message” arrives in our organization seconds after the external organizer canceled the meeting. So, we were handed a conversion – from email to appointment/meeting – issue.

After realizing that Exchange 2010 wasn’t converting the message to a meeting, I had to figure out why the delay was happening. The process of converting messages to a meeting should be done in two ways: At the Exchange Server level or at the Outlook level.

In order to Exchange Server 2010 convert the email to a meeting, there an attribute called ProcessExternalMeetingMessages which must be enabled to perform the conversion at the Exchange Server level. Otherwise the email will remain in the inbox folder showing as a message instead of appears in the calendar.

If this attribute isn’t enabled, Outlook by default will perform this conversion at the client level. Although the Outlook obviously must be opened.

Back to the related situation, I figured out that the manager used to open the Outlook just few times per week because he traveled a lot and always used the smartphone or OWA to access his mailbox. At the same time his mailbox attribute ProcessExternalMeetingMessages was set as false. That’s why his meetings took too long to appear or update.


The Exchange Server 2010 by default has the ProcessExternalMeetingMessages attribute set as false. To set this attribute as true you can perform the following command at the Exchange Shell:

Set-CalendarProcessing -Identity "Mailbox" -ProcessExternalMeetingMessages:$True

Or it also can be done using the ECP:

Process meeting

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