Last modified: July 23, 2011

Applies to: Outlook

Completes a message's recipient list, expanding particular distribution lists.

HRESULT ExpandRecips(
  LPMESSAGE lpMessage,
  ULONG FAR * lpulFlags


[in] A pointer to the message that has the recipient list to be processed.


[out] A pointer to a bitmask of flags that controls the type of processing that occurs. The following flags can be set:


The message needs to be preprocessed before it is sent.


The MAPI spooler (rather than the transport provider to which the caller is tightly coupled) must send the message.


The message's recipient list was successfully processed.

The IMAPISupport::ExpandRecips method is implemented for message store provider support objects. Message store providers call ExpandRecips to prompt MAPI to perform the following tasks:

  • Expand certain personal distribution lists to their component recipients.

  • Replace all display names that have been changed with the original names.

  • Mark any duplicate entries.

  • Resolve all one-off addresses.

  • Check whether the message needs preprocessing and, if it does, set the flag pointed to by lpulFlags to NEEDS_PREPROCESSING.

ExpandRecips expands any distribution lists that have the messaging address type of MAPIPDL.

Always call ExpandRecips as part of your message processing. Make a call to ExpandRecips one of the first calls in your IMessage::SubmitMessage method implementation.