.PST File Format – Templates and calculated properties

Properties every object must have

The attachment table exists only if the message has at least one attachment (mfHasAttach in PidTagMessageFlags); the number of attachment subnodes must equal its rows. A recipient table must exist for every message. Both live in the message node's subnode tree (found by NID_ATTACHMENT_TABLE and the recipient table NID).

Template tables

A template table is a table context with no rows and a fixed set of columns. Each PST has one for the folder hierarchy, contents and FAI tables, the search contents table, the recipient table and the attachment table. When a folder is created its three tables are duplicated from the templates, which gives their default columns; the Copied column says whether the property is copied from the child object into the table row when the child is created. Newer Outlook versions may add columns; the lists are the required ones. A parent's table rows duplicate properties of the child objects, so a change to a child must be reflected in the parent's table.

The RowIndex of these tables maps each row to its object: dwRowID is the NID of the sub-folder, message or attachment subnode and dwRowIndex its 0-based row in the row matrix.

Hierarchy table template (NID 0x60D)

Contents table template (NID 0x60E)

FAI contents table template (NID 0x60F)

Search folder contents table template (NID 0x610)

(0E07 PidTagMessageFlags and 0E17 PidTagMessageStatus appear twice in the specification's list; they are one column each.) The search update queue of a search folder (node type 0x06) is changed only through the search management queue and a reader must not modify it; the search criteria object (node type 0x07, a PC) must not be modified, and its properties are out of the scope of [MS-PST].

Recipient table template (NID 0x692)

A message's own recipient table has all these columns and more.

Attachment table template (NID 0x671)

Calculated properties

Properties a reader presents but the file does not store as such. Each row has a property tag, a base tag (the stored property it is derived from, nid or nidParent meaning that node field), and Get, Set, Delete and List behaviours. A reader must follow them. PC means the value is read from or written to the property context unchanged; N means not allowed.

List behaviour (when all properties are enumerated)

• ALWAYS: included. ALLOW: included only if the PC already has the property. BASED: included only if the base-tag property exists. BODY: included if any of PidTagRtfCompressed, PidTagBody, PidTagBodyHtml or PidTagHtml exists. NEVER: not included, but can still be got and, by the Set and Delete rules, changed.

Get behaviours

Set and delete behaviours

Subject handling

PidTagSubject is stored with optional metadata. If its first character (one byte in an ANSI PST, two in a Unicode one) has the value 1, the next character is the length of the prefix plus one (the prefix and its separator, usually a space); the normalised subject follows the prefix. The specification's ANSI example is the bytes 01 05 52 45 3A 32 53 55 42 00: the length field is 5 for a 4-character prefix (52 45 3A 32), so the normalised subject (SUB) starts at index 6. When writing, add 1 to the length. If the first character is not 1 the string is the whole subject with no metadata, and the prefix and normalised subject must be found by parsing: a prefix is one to three non-space, non-digit characters followed by a colon, then zero or more space characters (no other white space) before the normalised subject.

Calculated properties by object

Columns: tag, base tag if any, Get, Set, Delete, List. (ANSI and Unicode lists are the same except where the specification marks ANSI only.)

An embedded message has the same list as a message except that it has no PidTagMessageStatus, PidTagRtfInSync, Repl*, ProviderItemid, PidTagReplFolderid or PidTagShortTerm… and PidTagSubTreeContainer entries, and its PidTagSubject and PidTagSubjectPrefix have the Set codes exchanged relative to the message list (the specification lists SPSET_SUB for the subject and SPSET_SP for the prefix there).