DRIT.Mail 26.7.878

DRIT.Mail

Pure-Managed .NET Mail File-Format and Message-Security Library

Read, Write, Convert, Sign, and Verify Outlook/Exchange Mail Formats

DRIT.Mail is a pure-managed .NET library for reading, writing, converting, signing, encrypting, and verifying Outlook/Exchange mail file formats — MSG, PST, EML, iCalendar, vCard, and MBOX — with a first-class, source-level RFC implementation layer (MIME, S/MIME, DKIM, CMS, ASN.1, X.509, DNS, SMTP, POP3, IMAP).

Key Benefits

• Zero external dependencies – pure managed C# implementation, no Outlook installation required
• MAPI object model at the core – a message is a MapiMessage regardless of storage backend
• Cross-format conversion in one line – MSG ↔ PST ↔ EML ↔ iCal ↔ vCard
• Deep format fidelity – full PST NDB/LTP layer, in-house OLE Compound File engine
• Self-contained crypto stack – S/MIME and DKIM with no System.Security.Cryptography.Pkcs dependency
• DKIM verification (not just signing) with a built-in DNS client

Cross-Platform Mail Library

DRIT.Mail targets .NET Standard 2.0 and .NET Framework 4.8, so it runs on:

• Operating Systems: Windows, Linux, macOS
• Frameworks: .NET Standard 2.0, .NET Framework 4.8+, .NET Core / .NET 5+
• Dependencies: None – all functionality is built-in

Features

File Format I/O

• MSG (Outlook Item) – read/write via in-house OLE Compound File engine ([MS-OXMSG])
• PST (Personal Folders) – read/write with full NDB/LTP layer, ANSI/Unicode/Unicode-4k ([MS-PST])
• EML (Internet Message) – read/write via first-class MIME implementation (RFC 5322/2045–2049)
• MBOX (Mailbox Archive) – read/write, streaming, mboxrd (RFC 4155)
• ICS (iCalendar) – read/write with full component support (RFC 5545)
• VCF (vCard) – read/write, versions 2.1/3.0/4.0 (RFC 6350/2426)
• TNEF (winmail.dat) – parse

MAPI Object Model

• MapiMessage, MapiContact, MapiAppointment, MapiTask, MapiJournal, MapiNote, MapiMeeting, MapiRss
• Full MAPI property system – every PidTag* tag, named properties (GUID + string), multi-value properties
• RTF body (MS-OXRTFCP compressed, decompressed on read)
• Attachments – file, inline (Content-ID), embedded messages (AttachMethod == 5)

Cross-Format Conversion

14 conversion paths via the MailMessageConverter facade:

• PST ↔ MSG, MSG/PST ↔ EML, EML → MSG/PST
• MSG/PST ↔ iCal, MSG/PST ↔ vCard

Protocol Clients

• SMTP (RFC 5321) – STARTTLS, implicit TLS, SASL, XOAUTH2, pipelining, mass sending, DKIM integration
• POP3 (RFC 1939) – USER/PASS, APOP, SASL, STLS, implicit TLS, UIDL
• IMAP (RFC 9051/3501) – LOGIN + SASL, XOAUTH2, SELECT/EXAMINE, LIST/CREATE/DELETE/RENAME, FETCH, STORE, COPY/MOVE, SEARCH, IDLE, STATUS

Message Security

• S/MIME (RFC 5751) – sign (detached + opaque), verify, encrypt (AES-CBC + RSA), decrypt
• DKIM (RFC 6376) – sign and verify with built-in DNS client for key lookup
• CMS (RFC 5652), ASN.1 DER, X.509 – self-contained, no System.Security.Cryptography.Pkcs dependency
• DNS client (RFC 1035) – TXT record resolution for DKIM key lookup

Additional Capabilities

• PST search folders (SUD) and client-side content search
• File structure validation (PST, MSG, OLE Compound)
• Message comparison (property-level diffing)

Supported File Formats

Installation

1. Install via NuGet

• Open Microsoft Visual Studio and the NuGet package manager
• Search for "DRIT.Mail"
• Click Install to download and reference it in your project

2. Install via Package Manager Console

Install-Package DRIT.Mail

3. Install via .NET CLI

dotnet add package DRIT.Mail

Code Examples

Load and Convert a Message

using DRIT.Mail;

// Auto-detect format from the extension and load.
IMailMessage message = MailFile.Load("input.eml");

// Convert to MSG — one line, regardless of source format.
message.Save("output.msg", MailMessageFormat.Msg);

// Access the underlying MAPI object model.
MapiMessage mapi = message.MapiMessage;
Console.WriteLine("Subject: {0}", mapi.Subject);
foreach (MapiRecipient recipient in mapi.Recipients)
    Console.WriteLine("  {0}: {1}", recipient.RecipientType, recipient.EmailAddress);

Read a PST File

using DRIT.Mail;
using DRIT.Mail.Pst.PhysicalLayout;

PstFile pst = MailFile.OpenPst("archive.pst");

// Walk the folder hierarchy and export every message to MSG.
CompositeFolder root = pst.Folders.RootCompositeFolder;
foreach (CompositeFolder folder in root.GetDepthFirstFolderEnumerator())
{
    Console.WriteLine("Folder: {0}", folder.Folder.DisplayName);
    foreach (PstMapiMessage item in folder.GetMapiMessages())
        MailFile.Save(item, $"{item.Subject}.msg", MailMessageFormat.Msg);
}

Send a Message via SMTP

using DRIT.Mail.Rfc.Mime;
using DRIT.Mail.Rfc.Smtp;
using DRIT.Mail.Rfc.Smtp.Auth;

MimeMessage message = new MimeMessageBuilder()
    .From(new MailboxAddress("sender@example.com"))
    .To(new MailboxAddress("recipient@example.com"))
    .Subject("Hello from DRIT.Mail")
    .TextBody("This message was created and sent with DRIT.Mail.")
    .Build();

var options = new SmtpClientOptions("smtp.example.com", 587)
{
    Credentials = new SmtpCredentials("user", "password"),
    SslMode = SmtpSslMode.Auto,
};

using (var smtp = new SmtpClient(options))
{
    SmtpDeliveryResult result = smtp.Send(message);
    Console.WriteLine("Delivered: {0}", result.IsSuccessful);
}

Receive and Search via IMAP

using DRIT.Mail.Rfc.Imap;
using DRIT.Mail.Rfc.Sasl;

var options = new ImapClientOptions("imap.example.com", 993)
{
    Credentials = new SaslCredentials("user", "password"),
    SslMode = ImapSslMode.Auto,
};

using (var imap = new ImapClient(options))
{
    imap.Connect();
    imap.Authenticate();
    imap.SelectFolder("INBOX");

    // Server-side search: unseen messages since 2026-01-01.
    var criteria = ImapSearchCriteria.Create()
        .Unseen()
        .Since(new DateTimeOffset(2026, 1, 1, 0, 0, 0, TimeSpan.Zero));

    foreach (long uid in imap.Search(criteria))
    {
        MimeMessage message = imap.FetchMessage(
            ImapMessageSet.FromUids(new[] { uid }),
            ImapFetchOptions.Body);
        Console.WriteLine("[{0}] {1}", uid, message.Subject);
    }
}

S/MIME Sign and Verify

using DRIT.Mail.Rfc.SMime;
using DRIT.Mail.Rfc.Crypto.X509;

var certInfo = X509CertificateReader.ReadFromPem(File.ReadAllText("signer.pem"));
var signer = new SMimeSigner(new SMimeSignerOptions
{
    SignerCertificate = certInfo.Certificate,
    PrivateKey = certInfo.RsaPrivateKey,
    DigestAlgorithm = DigestAlgorithm.Sha256,
});

// Sign (detached / clear-signed produces multipart/signed).
MimeMessage signed = signer.SignDetached(message);

// Verify.
var verifier = new SMimeVerifier();
SMimeVerificationResult result = verifier.Verify(signed);
Console.WriteLine("Valid: {0}", result.IsValid);

System Requirements

• Target Frameworks: .NET Standard 2.0, .NET Framework 4.8+
• Dependencies: None – all mail, crypto, and protocol functionality is built-in

© 2026 DR-IT Ltd. All Rights Reserved.