Source Providers and their associated Source ID's are part of a mechanism that supports per-provider customization of the PIM experience on Windows Mobile devices.

A Source Provider is a custom function that customizes the PIM user experience. Typically, a Source Provider has a corresponding associate function that is responsible for synchronizing PIM data with the Windows Mobile device. Data synchronized with the Windows Mobile device by this associate function is marked with a Source identification tag (Source ID). When Outlook Mobile displays a PIM item, it checks to see if the item has a Source ID. If it finds one, it invokes the Source Provider, which customizes the user interface for the PIM item.

When users enter new contacts and appointments, they can select a Source Provider to associate with them.

A valid Source ID is a DWORD with only 1 bit set (i.e., there are 32 possible Source IDs).

Although Contactand Appointmentitems, regardless of Source ID, are synchronized with Microsoft Exchange — Source IDs are not.

Source IDs are not supported for Taskitems.

Since Contactsand Appointmentscan be associated with only one Source Provider, your Source Provider installation implementation must select a Source ID that is unique in the domain of all Source Providers installed on the Windows Mobile device (it is considered an error to determine Source IDs prior to install). Your implementation must choose a unique Source ID by first iterating over the installed Source Providers registered in the key \HKLM\PIMSources\, and then choosing the next available Source ID.

The default Source ID value is zero (0). Contactand Appointmentitems with a Source ID value of zero are not associated with a Source Provider, and just use the default user interface.

Your Source Provider uninstall implementation must reset the Source ID field of all associated Contactand Appointmentitems back to zero.