Did I Send That?

[This is now documented here: http://msdn.microsoft.com/en-us/library/ff960604.aspx ]

We had a customer here who wondered why messages imported into MAPI using MIMEToMAPI always appeared as draft messages. This is because the default value of PR_MESSAGE_FLAGS includes the MSGFLAG_UNSENT flag. Now - if you know you want your messages to not appear as drafts, the thing to do here is to clear the MSGFLAG_UNSENT flag before saving the message.

But what if you're exporting messages from mailbox using MAPIToMIMEStm and importing them using MIMEToMAPI, and want to preserve the sent/unsent state across this conversion? One thing you could do is read the state during the export, save it off somewhere (perhaps as a header in the EML file), then use it to determine if the flag needs to be cleared.

Doable - but a bit of extra work. Turns out there's  flag you can use in those functions that has nearly the same effect: CCSF_EMBEDDED_MESSAGE

Here's the documentation on the flag:

Flag value:

#define CCSF_EMBEDDED_MESSAGE 0x8000 // sent/unsent information is persisted in X-Unsent


When CCSF_EMBEDDED_MESSAGE is set, if PR_MESSAGE_FLAGS has the MSGFLAG_UNSENT flag set, add an X-Unsent header to the MIME message with a value of 1


When CCSF_EMBEDDED_MESSAGE is set, the resultant MAPI message will have MSGFLAG_READ set in PR_MESSAGE_FLAGS. In addition, if an X-Unsent header is found with a value of 1, the MSGFLAG_UNSENT flag is removed from PR_MESSAGE_FLAGS.


This flag may be used in Outlook 2003 and higher. The name of this flag reflects the way it originally was used, as a way to deal with embedded messages. It is no longer used in this fashion. If the side effect of setting MSGFLAG_READ is not desired, this flag should not be used. If this flag is not set, MIMEToMAPI will ignore any value in X-Unsent and MSGFLAG_UNSENT will be set in PR_MESSAGE_FLAGS. MAPIToMIMEStm will not write the X-Unsent header at all if the MSGFLAG_UNSENT flag is not set in PR_MESSAGE_FLAGS.

Comments (5)

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  1. Mahesh W says:

    I came across your post while searching for some other problem. I feel you may answer my query.

    I am trying to convert MSG file having 80 MB attachment into EML file. But the method IConverterSession::MAPIToMIMEStm takes lot of time (almost 10 minutes on my system) for conversion. Is there any way to convert the MSG into EML in faster way?

  2. It might go a lot faster if you’ve converted the MSG to a MAPI message in a store first. But that conversion itself may take a while – that’s a rather large message for the .MSG format.

  3. hms says:


    Do you know if  there is some other property that is "required" to be set along with an unset MSGFLAG_UNSENT.

    My attempts to unset this flag seem to be failing.


  4. vicky says:

    i have set the MSGFLAG_READ using SETREADFLAGS method.Now i want to check that flag for each message whether it is set or not.Please say some clue or any tries. I have spent 2 days searching this.

    Thanx & regards


  5. Vicky – get the PR_MESSAGE_FLAGS property from the message and check if the flag is set in there.

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