Creates a new message.
[in] A pointer to the interface identifier (IID) that represents the interface to be used to access the new message. Valid interface identifiers include IID_IUnknown, IID_IMAPIProp, IID_IMAPIContainer, and IID_IMAPIFolder. Passing NULL causes the message store provider to return the standard message interface, IMessage : IMAPIProp.
[in] A bitmask of flags that controls how the message is created. The following flags can be set:
The message to be created should be included in the associated contents table instead of the standard contents table. Associated messages are hidden from user interaction.
CreateMessage is allowed to succeed even if the create operation has not fully completed. This implies that the new message might not be immediately available to the caller.
[out] A pointer to a pointer to the newly created message.
You can choose whether to set all of the required message properties in CreateMessage or in the message's IMAPIProp::SaveChanges method. You do not have to make these properties available until a successful save has occurred.
Some message store providers allow the entry identifier of the new message to be available immediately after CreateMessage returns; others delay its availability until the message has been saved. Because not all message store providers generate an entry identifier for a new message until you have called the message's IMAPIProp::SaveChanges method, you may not be able to access the entry identifier when CreateMessage returns. Also, the new message may not be included in the folder's contents table until the save occurs.
Expect the entry identifier assigned to the new message to be unique not only in the current message store, but most likely across all of the message stores that are open concurrently. One exception to this rule occurs when multiple entries for a message store appear in the profile, which causes the message store to be opened multiple times and entry identifiers to be duplicated.
To create an outgoing message, call the Outbox folder's IMAPIFolder::CreateMessage method.
If you delete a folder that contains a new message before the message is saved, the results are undefined.