Thursday 7 June 2007

Appointments, meetings, invites, updates and responses

And so for my first proper (read: useful) post. This post was going to be about how Outlook's Sniffer works on calendar-related mail items - largely because this feature is pretty much undocumented and I find myself explaining it quite often. However, I realised there's some background information to cover first. I hear the terms appointment, meeting and invite used interchangably, which doesn't matter too much at a user level but can cause confusion when you try to troubleshoot calendar problems. In fact the three things are different, and it's useful to understand the distinction.
  • An appointment is an Outlook Calendar item
  • A meeting is an appointment with invitees
  • An invite is a mail item that tells Outlook to create a Calendar item (also known as a meeting request)

...and while I'm writing a mini-glossary of calendar terms...

  • An update is a mail item that tells Outlook to change a Calendar item
  • A response is a mail item that tells the user that someone accepted or declined their meeting, and tells Outlook to update the meeting's Tracking information

In fact, at the mailbox level, all of these (along with Tasks, Notes and pretty much anything else you can store in a mailbox) are messages regardless of their type or whether they live in your Calendar, Inbox or wherever. One day I'll write a post about different message types and how Outlook knows what to do with each, but it isn't important for the purpose of understanding how calendaring works.

Anyway, a typical calendar scenario might go like this...

  1. I decide to book a meeting with my colleagues Anne and Bob. I create a meeting item, and add them as invitees.
  2. When I've finished entering all the details, I hit Send. At this point, my meeting item is saved in the Calendar, and Outlook creates a meeting request (a type of mail item) containing the relevant details of the meeting, which it sends to Anne and Bob.
  3. Anne receives the invite in her Inbox. (Bob does too, but we're just looking at Anne's mailbox right now. Thankfully neither of them have delegates because this post is getting long enough without covering delegate behaviour - again, another post for another day.)
  4. On Anne's machine, Outlook's Inbox Sniffer - that's our undocumented friend that acts on certain types of message in your Inbox - sees a new invite has arrived so uses the details from it to create a new meeting item in her calendar, which it marks as Tentative.
  5. A few minutes later Anne sees the invite herself, opens it and clicks on Accept then chooses to send the response without editing it. At this point, Outlook creates a response (a type of mail item) which it sends back to me, and marks the meeting in Anne's calendar as Accepted.
  6. I receive the response item in my Inbox. The Sniffer sees it and marks Anne's Tracking status for the meeting as Accepted. Because I have the option selected to delete blank meeting responses after processing, it also deletes the response from my Inbox.

So far we've created two calendar entries (one in each of our calendars) and two message items (an invite and a response). This is the crux of mail-based calendaring, every action on one calendar has to be communicated to the other calendar(s) by messages. A point of note is that mail items arrive in the Inbox, meetings and appointments live in the Calendar. They're connected (Outlook has an identifier property on the original Calendar item which all the other items reference so it should always know which response or update refers to which meeting) but very much separate - knowing this is useful when trying to troubleshoot missing appointments, which at my place of work is something we spend a lot of time doing!

If I later decide to change the time of the meeting, I can change the meeting item in my Calendar, and send an update (another mail item) to Anne and Bob, which their Inbox Sniffer will process much the same as before. And again, they can send a response which my Inbox Sniffer will process.

There are pitfalls around this mail-based structure, especially if you bring a delegate into the mix (one meeting, one Calendar, but potentially two copies of the invites/updates and two sniffers... it's a recipe for confusion) and I guess that's something else to add to my ever-growing Topics For Future Posts list.

I said at the start of this post it would be useful. I'm not sure if it actually is directly useful but it should give an idea of how calendaring works in Outlook, which will be relevant when I post on more practical topics in future.

That's all for now



  1. Very useful comment. I would be really curious to read your next post on what happens with a delegate. I act as a delegate and it can get very funky. Outlook has lots of little glitches, which seem to really come out when a delegate gets involved, especially in my case where my manager never even sees the meeting requests. Only I see them! Thanks again for the post. Looking forward to the next one.

  2. Thanks for your comment, Courtney. The setting you're using "Send meeting requests and responses only to my delegates, not to me" is one of the ones I usually try to persuade people to use when we're troubleshooting a long-running 'problem' calendar. By not having the manager see the invites, you're reducing the opportunity for them to be mishandled by at least 50%! is a must-read for all delegates, I find about 99% of the usual calendar problems (missing appointments and loss of ownership of meetings) are avoided by strictly following the advice in there. Also see my other Outlook Calendar posts for some detailed information on specific scenarios where things commonly go wrong!


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