Creating a Message Subject

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The subject of a message, PR_SUBJECT (PidTagSubject), is an optional property, used to summarize the intent of a message. If you choose to set it, make it a character string 128 bytes or less. The 128 byte limit is not a limit imposed by MAPI; it is a limit imposed by some message store providers. To ensure interoperability with providers that do impose it, limit subjects to 128 bytes.

Be aware that some message store providers do not allow PR_SUBJECT to be written to a stream with the IStream interface.

Do not set PR_SUBJECT_PREFIX (PidTagSubjectPrefix); this property is set only on replies and forwarded messages.