private async Task SendEhlo(SmtpSender sender, Connection connection, CancellationToken cancellationToken)
{
sender.RequestText = $"{SmtpCommandNames.EHLO} {ClientHostname}";
await connection.WriteLineAsync(sender.RequestText, cancellationToken).ConfigureAwait(false);
do
{
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
}while (!sender.IsReplyOk);
sender.ValidateReply();
}
public ConnectionAuth(Connection connection, SmtpSender sender, NetworkCredential credentials)
{
_connection = connection;
_sender = sender;
_credentials = credentials;
}
/// <summary>
/// Sends an array of email messages using a session state object.
/// Credentials, Enable SSL and Client Hostname are NOT taken from the state object but
/// rather from the properties of this class.
/// </summary>
/// <param name="sessionStates">The session states.</param>
/// <param name="sessionId">The session identifier.</param>
/// <param name="callback">The callback.</param>
/// <param name="cancellationToken">The cancellation token.</param>
/// <returns>
/// A task that represents the asynchronous of send email operation.
/// </returns>
/// <exception cref="ArgumentNullException">sessionStates.</exception>
/// <exception cref="SecurityException">Could not upgrade the channel to SSL.</exception>
/// <exception cref="SmtpException">Defines an SMTP Exceptions class.</exception>
public async Task SendMailAsync(
IEnumerable <SmtpSessionState> sessionStates,
string?sessionId = null,
RemoteCertificateValidationCallback?callback = null,
CancellationToken cancellationToken = default)
{
if (sessionStates == null)
{
throw new ArgumentNullException(nameof(sessionStates));
}
using var tcpClient = new TcpClient();
await tcpClient.ConnectAsync(Host, Port, cancellationToken).ConfigureAwait(false);
using var connection = new Connection(tcpClient, Encoding.UTF8, "\r\n", true, 1000);
var sender = new SmtpSender(sessionId);
try
{
// Read the greeting message
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
// EHLO 1
await SendEhlo(sender, connection, cancellationToken).ConfigureAwait(false);
// STARTTLS
if (EnableSsl)
{
sender.RequestText = $"{SmtpCommandNames.STARTTLS}";
await connection.WriteLineAsync(sender.RequestText, cancellationToken).ConfigureAwait(false);
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
sender.ValidateReply();
if (await connection.UpgradeToSecureAsClientAsync(callback: callback).ConfigureAwait(false) == false)
{
throw new SecurityException("Could not upgrade the channel to SSL.");
}
}
// EHLO 2
await SendEhlo(sender, connection, cancellationToken).ConfigureAwait(false);
// AUTH
if (Credentials != null)
{
var auth = new ConnectionAuth(connection, sender, Credentials);
await auth.AuthenticateAsync(cancellationToken).ConfigureAwait(false);
}
foreach (var sessionState in sessionStates)
{
{
// MAIL FROM
sender.RequestText = $"{SmtpCommandNames.MAIL} FROM:<{sessionState.SenderAddress}>";
await connection.WriteLineAsync(sender.RequestText, cancellationToken).ConfigureAwait(false);
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
sender.ValidateReply();
}
// RCPT TO
foreach (var recipient in sessionState.Recipients)
{
sender.RequestText = $"{SmtpCommandNames.RCPT} TO:<{recipient}>";
await connection.WriteLineAsync(sender.RequestText, cancellationToken).ConfigureAwait(false);
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
sender.ValidateReply();
}
{
// DATA
sender.RequestText = $"{SmtpCommandNames.DATA}";
await connection.WriteLineAsync(sender.RequestText, cancellationToken).ConfigureAwait(false);
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
sender.ValidateReply();
}
{
// CONTENT
var dataTerminator = sessionState.DataBuffer
.Skip(sessionState.DataBuffer.Count - 5)
.ToText();
sender.RequestText = $"Buffer ({sessionState.DataBuffer.Count} bytes)";
await connection.WriteDataAsync(sessionState.DataBuffer.ToArray(), true, cancellationToken).ConfigureAwait(false);
if (!dataTerminator.EndsWith(SmtpDefinitions.SmtpDataCommandTerminator, StringComparison.OrdinalIgnoreCase))
{
await connection.WriteTextAsync(SmtpDefinitions.SmtpDataCommandTerminator, cancellationToken).ConfigureAwait(false);
}
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
sender.ValidateReply();
}
}
{
// QUIT
sender.RequestText = $"{SmtpCommandNames.QUIT}";
await connection.WriteLineAsync(sender.RequestText, cancellationToken).ConfigureAwait(false);
sender.ReplyText = await connection.ReadLineAsync(cancellationToken).ConfigureAwait(false);
sender.ValidateReply();
}
}
catch (Exception ex)
{
throw new SmtpException($"Could not send email - Session ID {sessionId}. {ex.Message}\r\n Last Request: {sender.RequestText}\r\n Last Reply: {sender.ReplyText}");
}
}