Duet provides a group policy setting named "Use Outlook settings for profile selection", which is designed to automatically select the default Outlook profile during Duet deployment if more than one profile exists. Duet deployment occurs the first time the Duet Utility runs after Duet has been installed on a machine. This policy setting sets the registry key:
HKCU\ Software\Policies\Microsoft\InformationBridgeFramework\Engine\Execution\UseDefaultProfile REG_DWORD = 1
But, there is a bug in the current logic in SP3 that prevents this from working on many machines. This issue will be fixed in the next hotfix or service pack to be released which should be available at the end of the month or beginning of November.
The problem is that Duet relies on a registry key, PickLogonProfile, that only exists on machines where someone has manually gone into Control Panel --> Mail --> Show Profiles, and changed the option to "Prompt for a profile to be used". Once changed the PickLogonProfile registry key gets created and is set to 1. Even if the control panel setting is changed back the PickLogonProfile key will remain - but it will get set to a value of 0.
This is the dialog from the Control Panel --> Mail --> Show Profiles
The registry key being set is:
1 = "Prompt for a profile to be used"
0 = "Always use this profile"
Doesn't Exist = "Always use this profile"
The reason that the UseDefaultProfile setting in Duet fails to pick the default profile is that Duet uses the PickLogonProfile registry key in the logic to determine if Duet should prompt for a profile. If users have Outlook configured to prompt for a profile every time they start Outlook then it also makes sense for Duet to prompt. But, Duet incorrectly assumes the PickLogonProfile registry key will exist on all machines when in fact it only exists on machines where the setting has been manually configured at some point. If PickLogonProfile doesn't exist Duet falls back to prompting the user instead.
If a workaround is needed before the next Duet hotfix is available, you can rollout the PickLogonProfile key to users if it doesn't already exist. This means doing a check to see if it is already configured with a value of 1. If it does exist, then leave it alone since we assume that a user has turned on this setting because they want to be prompted for a profile. If it does not exist or does not have a value of 1 then set it to 0. Once the PickLogonProfile key has been created with a value of 0 the Duet policy setting, UseDefaultProfile, should work without users being prompted to pick a profile.