Occasionally, Outlook rules can clash with OnINBOX, what might I expect to see if this is occurring?
Inbound emails getting duplicated, so they appear in the expected folder AND the main inbox as well.
Inbound emails appearing only in the inbox rather than the expected folder.
How can this be remedied?
The OnINBOX processing rule must be the last rule in the list and each rule that moves emails (except OnINBOX processing) must have "Stop processing more rules" checked.
The long version:
OnINBOX creates several components within the email environment to operate. These are the two folders, Processing and Quarantine, and the inbox processing rule.
The processing rule is the place where emails will sit before they have the A, C and T banner applied to them.
The quarantine folder is where emails are sent when they are reported by the user.
The inbox processing rule is to ensure that emails are moved to the Processing folder to start the process of adding the banner.
The OnINBOX processing rule, in some situations, will clash with other rules that move emails and, as an error handler for this, Outlook will create two emails. Other situations may result in the email ending up in the wrong place.
This can be fixed by changing the rules priority and one of the settings for each rule. Rules settings can be found by navigating to Settings>Email>Rules as shown below.
All rules that move emails must be above (at a high priority) OnINBOX's rule as shown below. You can move emails up and down the priority with the arrows on the right.
Additionally, "Stop processing more rules" should be ticked for every one of these rules (with the exception of OnINBOX processing) as shown below. You can access this setting by clicking the pencil to the right of each rule.
With the priorities set like this and "Stop processing more rules" ticked for all of your email moving rules, you should not see duplicated or out-of-place emails due to OnINBOX.