PSTFileFormat is an open source library written in C# designed to read and write to Outlook PST files.

Usage Examples:

List all folders in a PST file:

public void ListAllFolders(PSTFile file)
{
    tvFolders.Nodes.Clear();
    PSTFolder rootFolder = file.TopOfPersonalFolders;
    TreeNode rootNode = new TreeNode(rootFolder.DisplayName);
    rootNode.Name = rootFolder.NodeID.Value.ToString();
    tvFolders.Nodes.Add(rootNode);
    AddSubFolders(rootNode, rootFolder);
}

public void AddSubFolders(TreeNode node, PSTFolder folder)
{ 
    List<PSTFolder> childFolders = folder.GetChildFolders();
    foreach(PSTFolder childFolder in childFolders)
    {
        TreeNode childNode = new TreeNode(childFolder.DisplayName + " (" + childFolder.ItemType.ToString() + ")" );
        childNode.Name = childFolder.NodeID.Value.ToString();
        node.Nodes.Add(childNode);
        AddSubFolders(childNode, childFolder);
    }
}

Technical References:

1. https://msdn.microsoft.com/en-us/library/ff385210(v=office.12).aspx

2. https://blogs.msdn.microsoft.com/openspecification/2010/11/30/ms-pst-how-to-navigate-the-node-btree/

3. https://blogs.msdn.microsoft.com/openspecification/2011/02/11/ms-pst-the-relationship-between-nodes-and-blocks/

License:

PSTFileFormat is licensed under the GNU Lesser Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.