Read Outlook for Mac OLM File & Get Folders & SubFolders Information

OLM is a specific file format used by Microsoft Outlook for storing local data such as emails, attachments, notes, calendar data, contacts, tasks, history, and more. OLM files are only compatible with Outlook for Mac and cannot be opened or accessed by Outlook for Windows, which uses the PST file format instead.

Opening OLM format files

OLM format files can be opened in two ways:

  • using constructor
  • using static FromFile method

There are differences in behavior between these methods. See section below.

Opening files by constructor

To open a file, call constructor of the OlmStorage class and pass full file name or stream as an argument to it:

var fileName = "MyStorage.olm";
var olm = new OlmStorage(fileName);

Opening files using static method FromFile

To open a file, use static method FromFile and pass full file name or stream as an argument to it:

var fileName = "MyStorage.olm";
var olm = OlmStorage.FromFile(fileName);

Getting folders

To access the directory structure of an OLM file, create an instance of the OlmStorage class using its constructor and pass in the path to the file. Once the file is open, access its directory structure using the FolderHierarchy property. This property returns a list of OlmFolder objects, each representing a directory in the OLM file. To further explore the directory structure, access the SubFolders property of each object, which returns a list of its subdirectories. By using these properties, you can navigate through the entire directory hierarchy of the OLM file and access all the directories and subdirectories it contains.

The example below displays the list of all folders in hierarchical order:

using (var olm = new OlmStorage(fileName))
{
    PrintAllFolders(olm.FolderHierarchy, string.Empty);
}

private void PrintAllFolders(List<OlmFolder> folderHierarchy, string indent)
{
    foreach (var folder in folderHierarchy)
    {
        Console.WriteLine($"{indent}{folder.Name}");
        PrintAllFolders(folder.SubFolders, indent+"-");
    }
}

When using the FromFile method to open an OLM file, the FolderHierarchy property will not be initialized by default and will return null. In this case, call the GetFolders method explicitly to initialize the FolderHierarchy property and retrieve the list of directories in the OLM file:

using (var olm = OlmStorage.FromFile(fileName))
{
    var folders = olm.GetFolders();
}

Also, it’s possible to get any folder by name:

  1. Call GetFolder method.
  2. Pass folder name as the first argument and value, which shows whether to ignore case sensitivity when searching for a folder, as the second parameter.
using (var olm = OlmStorage.FromFile(fileName))
{
    // get inbox folder by name
    OlmFolder folder = olm.GetFolder("Inbox", true);
}

List of emails

OlmFolder class, which represents a folder, has the following methods to get the list of emails:

  • EnumerateMessages implements iteration of emails in a folder. In this case, every iteration returns OlmMessageInfo object, which provides short info about email.
  • EnumerateMapiMessages, also implements iteration of emails in a folder, but in this case, every iteration returns MapiMessage object, which represents the email itself, with all properties.

Using EnumerateMessages method

using (var olm = OlmStorage.FromFile(fileName))
{
    var folder = olm.GetFolder("Inbox", true);
    foreach (var messageInfo in folder.EnumerateMessages())
    {
        Console.WriteLine(messageInfo.Subject);
    }
}

Using EnumerateMapiMessages method

using (var olm = OlmStorage.FromFile(fileName))
{
    var folder = olm.GetFolder("Inbox", true);

    foreach (var msg in folder.EnumerateMapiMessages())
    {
        // save message in MSG format
        msg.Save($"{msg.Subject}.msg");
    }
}

Other useful properties

The other useful properties of the OlmFolder class are: HasMessages and MessageCount properties, which return the presence of messages in the folder and their count.

using (var olm = OlmStorage.FromFile(fileName))
{
    var folder = olm.GetFolder("Inbox", true);

    if (folder.HasMessages)
    {
        Console.WriteLine($"Message count: {folder.MessageCount}");
    }
}

Get or Set the Modified Date of a Message

The modified date represents the date and time when the OLM message was last modified. You can use the OlmMessageInfo.ModifiedDate property to retrieve or update the modified date value of an OLM message.

Here’s an example that demonstrates the usage of the property:

foreach (OlmMessageInfo messageInfo in inboxFolder.EnumerateMessages())
{
   DateTime modifiedDate = messageInfo.ModifiedDate;
}

Extracting emails

OlmStorage class has ExtractMapiMessage method which allows to extract emails. This method receives an OlmMessageInfo object.

using (var olm = OlmStorage.FromFile(fileName))
{
    var folder = olm.GetFolder("Inbox", true);

    foreach (var messageInfo in folder.EnumerateMessages())
    {
        if (messageInfo.Date == DateTime.Today)
        {
            // Extracts today's messages form Inbox
            var msg = olm.ExtractMapiMessage(messageInfo);
        }
    }
}

Extracting all Items from an Email using Traversal API

You can extract all items from an Outlook OLM file as far as possible, without throwing out exceptions, even if some data of the original file is corrupted. To perform this, use OlmStorage(TraversalExceptionsCallback callback) constructor and Load(string fileName) method instead of FromFile method. The constructor allows defining a callback method.

using (var olm = new OlmStorage((exception, id) => { /* Exception handling  code. */ }))

The callback method makes loading and traversal exceptions available.

The Load method returns ‘true’ if the file has been loaded successfully and further traversal is possible. If a file is corrupted and no traversal is possible, ‘false’ is returned.

if (olm.Load(fileName))

The following code snippet and the steps show how to use this API:

  1. Create a new instance of the OlmStorage class, passing an exception handling callback to handle any exceptions encountered during the process.
  2. Load the OLM file by calling the Load method of the OlmStorage instance.
  3. If the OLM file is successfully loaded, obtain the folder hierarchy by calling the GetFolders method on the OlmStorage instance. This returns a list of OlmFolder objects.
  4. Call the ExtractItems method, passing the OlmStorage instance and the list of OlmFolder objects.
  5. In the ExtractItems method, iterate through each folder in the folders list.
  6. If the folder contains messages (emails), print the folder name to the console using Console.WriteLine(folder).
  7. Iterate through the messages in the current folder by calling the EnumerateMessages method on the OlmStorage instance, passing the current folder as an argument.
  8. Print the subject of each message to the console using Console.WriteLine(msg.Subject).
  9. If the folder has subfolders, recursively call the ExtractItems method again, passing the OlmStorage instance and the subfolders of the current folder.
using (var olm = new OlmStorage((exception, id) => { /* Exception handling  code. */ }))
{
    if (olm.Load(fileName))
    {
        var folderHierarchy = olm.GetFolders();
        ExtractItems(olm, folderHierarchy);
    }
}

private static void ExtractItems(OlmStorage olm, List<OlmFolder> folders)
{
    foreach (var folder in folders)
    {
        if (folder.HasMessages)
        {
            Console.WriteLine(folder);

            foreach (var msg in olm.EnumerateMessages(folder))
            {
                Console.WriteLine(msg.Subject);
            }
        }

        if (folder.SubFolders.Count > 0)
        {
            ExtractItems(olm, folder.SubFolders);
        }
    }
}

Extract Messages from OLM by Identifiers

The process of email extraction has become easier with the ability to extract selected OLM messages by identifiers. It is urgent for applications storing identifiers in a database. Extracting messages on demand is the efficient way to avoid traversing through the entire storage each time to find a specific message to extract. The EntryId property of the OlmMessageInfo class gets the message entry identifier. The overloaded ExtractMapiMessage(string id) method of the OlmStorage class gets the message from OLM. The following code snippet demonstrates the use of these features:

foreach (OlmMessageInfo msgInfo in olmFolder.EnumerateMessages())
{
    MapiMessage msg = storage.ExtractMapiMessage(msgInfo.EntryId);
}

Get Folder Path

You may also get the folder path of folders in the OML file. Aspose.Email provides OlmFolder.Path property which returns the folder path. The following code snippet demonstrates the use of OlmFolder.Path property to get the folder paths in the OML file.

var storage = new OlmStorage("SampleOLM.olm");
PrintPath(storage, storage.FolderHierarchy);

public static void PrintPath(OlmStorage storage, List<OlmFolder> folders)
{
    foreach (OlmFolder folder in folders)
    {
        // print the current folder path
        Console.WriteLine(folder.Path);

        if (folder.SubFolders.Count > 0)
        {
            PrintPath(storage, folder.SubFolders);
        }
    }
}

Count the number of items in the folder

You may also count the number of items in the folder. Aspose.Email provides OlmFolder.MessageCount property which returns the number of items in the folder. The following code snippet demonstrates the use of OlmFolder.MessageCount property to get the number of items in the folders of the OML file.

var storage = new OlmStorage("SampleOLM.olm");
PrintMessageCount(storage.FolderHierarchy);

public static void PrintMessageCount(List<OlmFolder> folders)
{
    foreach (OlmFolder folder in folders)
    {
        Console.WriteLine("Message Count [" + folder.Name + "]: " + folder.MessageCount);
    }
}

Get Total Items Count of OlmStorage

OlmStorage class also has GetTotalItemsCount() method which returns the total number of message items contained in the OLM storage.

  using (var olm = new OlmStorage("storage.olm"))
  {
     var count = olm.GetTotalItemsCount();
  }

Extract messages from OLM by identifiers

Sometimes it is required to extract selected messages by identifiers. For example, your application stores identifiers in a database and extracts a message on demand. This is the efficient way to avoid traversing through the entire storage each time to find a specific message to extract. This feature is available for OLM storages.

The code below shows how to extract messages from OLM by identifiers.

The code performs the following steps:

  1. Initiates a foreach loop to iterate through a list of OlmMessageInfo objects. The loop uses the EnumerateMessages method of the olmFolder object to retrieve a list of all messages in the current folder being iterated.
  2. The loop extracts the corresponding MapiMessage object from the storage by calling the ExtractMapiMessage(string id) method of OlmStorage class, passing in the EntryId of the current message as a parameter.

The retrieved MapiMessage object can be used to access and manipulate the contents of the message. The loop continues until all messages in the folder have been processed.

  foreach (OlmMessageInfo msgInfo in olmFolder.EnumerateMessages())
  {
      MapiMessage msg = storage.ExtractMapiMessage(msgInfo.EntryId);
  }
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