Aspose.Email FOSS
.NET
Developer Guide
MAPI Properties

MAPI Properties

MAPI Properties

This guide shows how to read, iterate, and write MAPI properties in Outlook MSG files using Aspose.Email FOSS for .NET. Every MSG file stores data as tagged key-value pairs; access them through MapiMessage, MapiPropertyCollection, and the CommonMessagePropertyId enum.

Reading Properties

Convenience Properties

MapiMessage exposes the most common properties as typed C# properties:

using Aspose.Email.Foss.Msg;

using var message = MapiMessage.FromFile("sample.msg");

Console.WriteLine(message.Subject);              // string?
Console.WriteLine(message.Body);                 // string?
Console.WriteLine(message.HtmlBody);             // string?
Console.WriteLine(message.SenderName);           // string?
Console.WriteLine(message.SenderEmailAddress);   // string?
Console.WriteLine(message.InternetMessageId);    // string?
Console.WriteLine(message.MessageDeliveryTime);  // DateTime?
Console.WriteLine(message.MessageClass);         // string?

Raw Property Access

For properties not exposed as typed convenience fields, call GetPropertyValue() with the property ID, type code, and a decode flag to retrieve the raw value:

// Read a string property by ID and type
var displayTo = message.GetPropertyValue(
    (ushort)CommonMessagePropertyId.DisplayTo,
    (ushort)PropertyTypeCode.PtypString,
    decode: true);

Console.WriteLine($"Display To: {displayTo}");

Iterate All Properties

Call IterPropertyKeys() to enumerate all (property ID, type) pairs, or use IterProperties() to get the full property objects including tag and decoded value:

// List all property keys (ID + type pairs)
foreach (var (propId, propType) in message.IterPropertyKeys())
    Console.WriteLine($"Property: 0x{propId:X4} (type: 0x{propType:X4})");

// Iterate full property objects
foreach (var prop in message.IterProperties())
{
    Console.WriteLine($"ID=0x{prop.PropertyId:X4} " +
                      $"Type=0x{prop.PropertyType:X4} " +
                      $"Tag=0x{prop.PropertyTag:X8} " +
                      $"Value={prop.Value}");
}

Writing Properties

Set Properties on a New Message

Create a MapiMessage with MapiMessage.Create(), then call SetProperty() with a CommonMessagePropertyId constant, a PropertyTypeCode, and the value to set:

var message = MapiMessage.Create("Test", "Body");

message.SetProperty(
    (ushort)CommonMessagePropertyId.SenderName,
    (ushort)PropertyTypeCode.PtypString,
    "Alice");

message.SetProperty(
    (ushort)CommonMessagePropertyId.SenderEmailAddress,
    (ushort)PropertyTypeCode.PtypString,
    "alice@example.com");

message.SetProperty(
    (ushort)CommonMessagePropertyId.MessageDeliveryTime,
    (ushort)PropertyTypeCode.PtypTime,
    new DateTime(2026, 3, 15, 10, 30, 0, DateTimeKind.Utc));

Direct Collection Access

MapiPropertyCollection exposes Add, Set, Get, and Remove methods for fine-grained control over individual MAPI properties without going through the typed convenience API:

// Access the property collection
var props = message.Properties;

// Add a property
props.Add(
    (ushort)CommonMessagePropertyId.InternetCodepage,
    (ushort)PropertyTypeCode.PtypInteger32,
    65001,  // UTF-8
    flags: 0);

// Read it back
var codepage = props.Get(
    (ushort)CommonMessagePropertyId.InternetCodepage,
    (ushort)PropertyTypeCode.PtypInteger32);

Console.WriteLine($"Codepage: {codepage?.Value}");

// Remove a property
props.Remove(
    (ushort)CommonMessagePropertyId.InternetCodepage,
    (ushort)PropertyTypeCode.PtypInteger32);

Common Property IDs

The CommonMessagePropertyId enum lists property IDs. Pass these constants to GetPropertyValue and SetProperty instead of numeric literals:

PropertyDescription
SubjectMessage subject
BodyPlain text body
BodyHtmlHTML body
SenderNameSender display name
SenderEmailAddressSender email address
DisplayToTo recipients display string
DisplayCcCc recipients display string
DisplayBccBcc recipients display string
InternetMessageIdRFC 5322 Message-ID
MessageDeliveryTimeDelivery timestamp
TransportMessageHeadersRaw RFC 5322 headers
AttachFilenameShort attachment filename
AttachLongFilenameLong attachment filename
AttachMimeTagAttachment MIME type
AttachContentIdAttachment Content-ID

Property Type Codes

The PropertyTypeCode enum maps MAPI type codes:

TypeDescription
PtypStringUnicode string
PtypString8ANSI string
PtypInteger3232-bit integer
PtypInteger6464-bit integer
PtypBooleanBoolean
PtypTimeDateTime (FILETIME)
PtypBinaryByte array
PtypGuidGUID

Attachment Properties

Each MapiAttachment also has its own Properties collection. Iterate attachment.Properties.IterProperties() to enumerate all MAPI property entries for that attachment:

foreach (var attachment in message.Attachments)
{
    Console.WriteLine($"Attachment: {attachment.Filename}");

    foreach (var prop in attachment.Properties.IterProperties())
        Console.WriteLine($"  0x{prop.PropertyTag:X8} = {prop.Value}");
}

See Also

See Also

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