Rebex MSG

Outlook MSG file format library for .NET

Download 30-day free trial Buy from $199
More .NET components

Back to feature list...

Standards and platform support

100% managed .NET code with no external dependencies 

  • Rebex MSG is written in 100% managed C# code.
  • No external dependencies. It only needs .NET.
  • No third-party or open source code used.
  • Fully CLS-compliant.
  • Supports any .NET language (C#, VB.NET, C++/CLI, etc.)
  • Platform-independent code. Same assemblies for both 32-bit and 64-bit applications and x86/x64, ARM32/ARM64 architectures.

.NET 7.0/6.0/5.0 

Rebex MSG supports .NET 7.0, .NET 6.0 and .NET 5.0 on all supported operating systems:

  • Windows 11 (x64, ARM64)
  • Windows 10 (x64, x86, ARM64)
  • Windows Server 2022 (x64)
  • Windows Server 2019 (x64)
  • Windows Server 2016 (x64)
  • Windows Server 2012 R2 (x64, x86)
  • Windows 8.1 (x64, x86)
  • Windows 7 SP1 (x64, x86) (end-of-life platform)
  • Linux (x64, ARM64, ARM32)
  • macOS (x64, ARM64)
  • Android (x64, ARM64, ARM32)
  • iOS/tvOS (x64, ARM64, ARM32)

.NET Framework on Windows 

Rebex MSG supports the following .NET Framework platforms:

  • .NET Framework 4.8.x
  • .NET Framework 4.7.x
  • .NET Framework 4.6.x
  • .NET Framework 4.5.x
  • .NET Framework 4.0
  • .NET Framework 3.5 SP1
  • Both 32-bit and 64-bit versions (same DLLs)

Legacy binaries for .NET Framework 2.0/3.0 are available as well.
For details and a trial version download link, see Support for Legacy Platforms.

Supported IDE versions:

  • Microsoft Visual Studio 2022
  • Microsoft Visual Studio 2019
  • Microsoft Visual Studio 2017
  • Microsoft Visual Studio 2015
  • Microsoft Visual Studio 2013
  • Microsoft Visual Studio 2012

Supported Windows versions:

Rebex MSG is also known to work on Windows 8, Windows Vista SP1, Windows XP SP3, Windows Server 2003 R2, Windows Embedded Standard 2009 and Windows Embedded POSReady 2009. However, these platforms already reached end-of-life (most of them many years ago), which means we cannot guarantee support for Rebex MSG on these operating systems.

.NET Core 

Rebex MSG supports .NET Core platform.

Supported versions:

Supported operating systems:

.NET Standard 

Rebex MSG supports .NET Standard 2.1 on .NET 7.0/6.0/5.0, .NET Core 3.1, Mono 6.10 (or higher), Xamarin.Android 10.1 (or higher) and Xamarin.iOS 13.10 (or higher). It also supports .NET Standard 2.0 on .NET Core 2.1.

Mono on Linux 

Rebex MSG supports Mono 6.0 (or higher) on Linux and macOS.


  • Visual Studio with Xamarin.iOS 13.10 or later
  • iOS 10.2 or later

To target Xamarin.iOS platform, reference .NET Standard 2.1 binaries.


  • Visual Studio with Xamarin.Android 10.1 or later

To target Xamarin.Android platform, reference .NET Standard 2.1 binaries.

MSG and RFC specifications 

Rebex MSG implements Outlook .MSG message structures as described by the following Microsoft documents:

In addition to Outlook .MSG API, Rebex MSG also provides Rebex.Mail assembly that provides a MIME and S/MIME API. and aims to implement the following Internet standards (MIME, S/MIME and CMS):

While we tried hard to be compliant with relevant RFCs, current practice in Internet mail often deviates from these standards. In fact, sometimes being compliant can severely hinder interoperability with existing software. Interoperability was therefore the highest priority.

Outlook MSG, MIME, S/MIME and other email formats 

E-mail message format supported by MsgMessage class (Rebex.Msg assembly):

  • Outlook MSG - native format used by Microsoft Outlook

E-mail message formats supported by MailMessage class (Rebex.Mail assembly):

  • RFC 822/2822/5322 - Internet Message Format
  • MIME - Multipurpose Internet Mail Extensions
  • MS-TNEF/winmail.dat - Microsoft's proprietary email extension format
  • Outlook MSG - native format used by Microsoft Outlook
Please note that although MailMessage class supports Outlook MSG on input and output as well, the class is MIME-based internally. When a MSG message is loaded into that class, it is converted to MIME internally, and when a MSG message is saved, it's converted from MIME again.

XCOPY deployment 

When distributing an application using Rebex MSG library, simply copy the following DLL files (.NET assemblies) with your application:

  • Rebex.Common.dll
  • Rebex.Mail.dll
  • Rebex.Msg.dll

There is no need to install, configure or distribute anything else to make them work.

Rebex MSG license is royalty-free - you can distribute your application to unlimited number of users or computers without any additional fees.

Back to feature list...