C# SMTP 대량메일 보내기

출처 : Code Snipet

C# SMTP로 대량 메일 발송하기.

Soket 이용

It’s easy to use System.net.mail namespace to send emails from asp.net. But the problem is system.net.mail.send() method does not close the connection to SMTP server. This is causing SMTP 4.2.2 error if you try to send multiple emails. While as per Microsoft this issue has been resolved in .net Framework 4.0 but people who are using 3.5 its still the issue. The workaround is to use sockets and System.Web.Mail namespace. Here is the sample code to send SMTP email using C# 3.5 -

workaround may be set maxtimeout=1

.NET Framework 4.0 has new property called SMTPClient.Dispose() to fix the issue

001	using System;

002	using System.Text;

003	using System.IO;

004	using System.Net.Sockets;

005	using System.Net;

006	using System.Web.Mail;

007

008	namespace mySMTP

009

{

010	/// <summary>

011	/// provides methods to send email via smtp direct to mail server

012	/// </summary>

013	public class SmtpDirect

014

{

015	/// <summary>

016	/// Get / Set the name of the SMTP mail server

017	/// </summary>

018	private static string SmtpServer = "outbound-mail.yourorg.com";

019	private enum SMTPResponse : int

020

{

021	CONNECT_SUCCESS = 220,

022	GENERIC_SUCCESS = 250,

023	DATA_SUCCESS = 354,

024	QUIT_SUCCESS = 221

025

}

026	public static bool Send(MailMessage message)

027

{

028	IPHostEntry IPhst = Dns.Resolve(SmtpServer);

029	IPEndPoint endPt = new IPEndPoint(IPhst.AddressList[0], 25);

030	Socket s = new Socket(endPt.AddressFamily, SocketType.Stream, ProtocolType.Tcp);

031	s.Connect(endPt);

032

033	if (!Check_Response(s, SMTPResponse.CONNECT_SUCCESS))

034

{

035	s.Close();

036	return false;

037

}

038

039	Senddata(s, string.Format("HELO {0}\r\n", Dns.GetHostName()));

040	if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))

041

{

042	s.Close();

043	return false;

044

}

045

046	Senddata(s, string.Format("MAIL From: {0}\r\n", message.From));

047	if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))

048

{

049

050	s.Close();

051	return false;

052

}

053

054	string _To = message.To;

055	string[] Tos = _To.Split(new char[] { ';' });

056	foreach (string To in Tos)

057

{

058	Senddata(s, string.Format("RCPT TO: {0}\r\n", To));

059	if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))

060

{

061	s.Close();

062	return false;

063

}

064

}

065

066	if (message.Cc != null)

067

{

068	Tos = message.Cc.Split(new char[] { ';' });

069	foreach (string To in Tos)

070

{

071	Senddata(s, string.Format("RCPT TO: {0}\r\n", To));

072	if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))

073

{

074	s.Close();

075	return false;

076

}

077

}

078

}

079

080	StringBuilder Header = new StringBuilder();

081	Header.Append("From: " + message.From + "\r\n");

082	Tos = message.To.Split(new char[] { ';' });

083	Header.Append("To: ");

084	for (int i = 0; i < Tos.Length; i++)

085

{

086	Header.Append(i > 0 ? "," : "");

087	Header.Append(Tos[i]);

088

}

089	Header.Append("\r\n");

090	if (message.Cc != null)

091

{

092	Tos = message.Cc.Split(new char[] { ';' });

093	Header.Append("Cc: ");

094	for (int i = 0; i < Tos.Length; i++)

095

{

096	Header.Append(i > 0 ? "," : "");

097	Header.Append(Tos[i]);

098

}

099	Header.Append("\r\n");

100

}

101	Header.Append("Date: ");

102	Header.Append(DateTime.Now.ToString("ddd, d M y H:m:s z"));

103	Header.Append("\r\n");

104	Header.Append("Subject: " + message.Subject + "\r\n");

105	Header.Append("X-Mailer: SMTPDirect v1\r\n");

106	string MsgBody = message.Body;

107	if (!MsgBody.EndsWith("\r\n"))

108	MsgBody += "\r\n";

109	if (message.Attachments.Count > 0)

110

{

111	Header.Append("MIME-Version: 1.0\r\n");

112	Header.Append("Content-Type: multipart/mixed; boundary=unique-boundary-1\r\n");

113	Header.Append("\r\n");

114	Header.Append("This is a multi-part message in MIME format.\r\n");

115	StringBuilder sb = new StringBuilder();

116	sb.Append("--unique-boundary-1\r\n");

117	sb.Append("Content-Type: text/plain\r\n");

118	sb.Append("Content-Transfer-Encoding: 7Bit\r\n");

119	sb.Append("\r\n");

120	sb.Append(MsgBody + "\r\n");

121	sb.Append("\r\n");

122

123	foreach (object o in message.Attachments)

124

{

125	MailAttachment a = o as MailAttachment;

126	byte[] binaryData;

127	if (a != null)

128

{

129	FileInfo f = new FileInfo(a.Filename);

130	sb.Append("--unique-boundary-1\r\n");

131	sb.Append("Content-Type: application/octet-stream; file=" + f.Name + "\r\n");

132	sb.Append("Content-Transfer-Encoding: base64\r\n");

133	sb.Append("Content-Disposition: attachment; filename=" + f.Name + "\r\n");

134	sb.Append("\r\n");

135	FileStream fs = f.OpenRead();

136	binaryData = new Byte[fs.Length];

137	long bytesRead = fs.Read(binaryData, 0, (int)fs.Length);

138	fs.Close();

139	string base64String = System.Convert.ToBase64String(binaryData, 0, binaryData.Length);

140

141	for (int i = 0; i < base64String.Length; )

142

{

143	int nextchunk = 100;

144	if (base64String.Length - (i + nextchunk) < 0)

145	nextchunk = base64String.Length - i;

146	sb.Append(base64String.Substring(i, nextchunk));

147	sb.Append("\r\n");

148	i += nextchunk;

149

}

150	sb.Append("\r\n");

151

}

152

}

153	MsgBody = sb.ToString();

154

}

155

156	Senddata(s, ("DATA\r\n"));

157	if (!Check_Response(s, SMTPResponse.DATA_SUCCESS))

158

{

159	s.Close();

160	return false;

161

}

162	Header.Append("\r\n");

163	Header.Append(MsgBody);

164	Header.Append(".\r\n");

165	Header.Append("\r\n");

166	Header.Append("\r\n");

167	Senddata(s, Header.ToString());

168	if (!Check_Response(s, SMTPResponse.GENERIC_SUCCESS))

169

{

170	s.Close();

171	return false;

172

}

173

174	Senddata(s, "QUIT\r\n");

175	Check_Response(s, SMTPResponse.QUIT_SUCCESS);

176	s.Close();

177	return true;

178

}

179	private static void Senddata(Socket s, string msg)

180

{

181	byte[] _msg = Encoding.ASCII.GetBytes(msg);

182	s.Send(_msg, 0, _msg.Length, SocketFlags.None);

183

}

184	private static bool Check_Response(Socket s, SMTPResponse response_expected)

185

{

186	string sResponse;

187	int response;

188	byte[] bytes = new byte[1024];

189	while (s.Available == 0)

190

{

191	System.Threading.Thread.Sleep(100);

192

}

193

194	s.Receive(bytes, 0, s.Available, SocketFlags.None);

195	sResponse = Encoding.ASCII.GetString(bytes);

196	response = Convert.ToInt32(sResponse.Substring(0, 3));

197	if (response != (int)response_expected)

198	return false;

199	return true;

200

}

201

}

202

203

}

Usage

1	string sBody = string.Empty;

2	System.Web.Mail.MailMessage message = new System.Web.Mail.MailMessage();

3	message.From = "def@hotmail.com";

4	message.To="abc@yahoo.com";

5	message.Subject = "Hello subject";

6	sBody = "Hello World" ;

7	mySMTP.Send(message)