- Meeting invites (adding tentative meetings to your calendar)
- Meeting updates (updating details in your calendar)
- Task updates
- Message recall (when someone recalls a message you've received)
- Responses to voting buttons (when you sent a mail with voting buttons, this adds the voting responses back to the original item)
This applies to Outlook versions from 2000 onwards. The results are slightly different in Outlook 2007 (e.g. the way meeting updates are processed) but - as far as I know - the mechanism is the same.
The Sniffer runs as a MAPI idle process. This means it starts processing when the messaging system that underlies Outlook isn't otherwise busy. This doesn't necessarily correspond to whether the Outlook application is busy though. You could be typing an email message and the Sniffer would still fire, whereas it won't fire if mail is downloading from a server, even though you're not 'using' Outlook at the time. This is why sometimes invites appear to show up as tentative Calendar entries almost straight away, and sometimes they take a little longer.
So far so good... but what do you do if the Sniffer isn't working?
(This bit bit contains technical advice, so my usual disclaimer applies.)
First, is the actionable item actually in the Inbox? If, say, a meeting invite got moved to a folder by a rule then it may have left the Inbox before the Sniffer got to it. If the rule is client-side then you could get a Rule vs. Sniffer race occurring.
Next, have you told Outlook not to process some item types? The settings Process requests and responses on arrival and Process receipts on arrival need to be selected (Tools > Options > Email options > Tracking Options) for those actions to take place.
- Is this machine able to run the Sniffer against this mailbox? To deal with users running Outlook on more than one machine with the same mailbox, a mechanism was put in place where only one can be the Sniffer at a time (the Sniff Owner). Run Outlook with the /sniff switch to set it as the Sniff Owner, or /cleansniff to delete and recreate the Sniff Owner information.
- Is there any idle time? An add-in or another application calling Outlook could be keeping MAPI busy (or making it think it's busy). Try closing down any applications that may interact with Outlook, e.g. synchronisation tools, and waiting at least five minutes before checking if items have been processed. If that didn't isolate the problem, try disabling any add-ins you have loaded in Outlook, wait five minutes and check again.
- Is thre a long idle time specified in the registry? Under the key HKEY_Current_User/Software/Microsoft/Office/11.0/Outlook/Options/General check for these values
- AutoProcessIdleTime - this is how much idle time is required before the Sniffer will act
- AutoProcessIdleTimeMax - this is how long the Sniffer waits before trying again if MAPI was not idle on the previous attempt
- Both the values are specified in milliseconds (so a value of 10000 is 10 seconds). If these don't exist in the registry then the defaults are used, 30 seconds and 600 seconds respectively. Setting a lower value for both would cause the Sniffer to run more frequently, but there would be an associated performance hit on the rest of Outlook. Setting the value very low would cause the Sniffer to run almost continuously, taking up system resources that could be used for other tasks.
- Is another application or add-in marking the items as 'sniffed'? This is the least likely scenario but theoretically could happen. To test for this you would need to look at the message properties of the Inbox item using a tool such as MDBVU or MFCMAPI. If the PR_PROCESSED property is set to TRUE then the Sniffer will not act on this item again because it thinks it has already done so. (If the property doesn't exist or is set to FALSE then the message has not been marked as sniffed.)
That covers just about everything I know about the Sniffer - I hope this post has been useful to someone out there!