There are two ways to do SMTP over SSL: Explicit and Implicit. Explicit means you connect to a normal SMTP port (usually 25 or 587) in plaintext, then issue the “starttls” command to switch to SSL-mode. Implicit means you connect to a port that expects everything to be SSL (usually 465).
Asp.net use “System.Net.Mail.SmtpClient()” to send Email. The main problem is SmtpClient does not support implicit SSL connections, but does support explicit connections (System.Net.Mail with SSL to authenticate against port 465). So, if the mail server(SMTP) do not support Explicit connection, it fails to send email and show messages like “Connection timeout“, “The message could not be sent to the SMTP server. The transport error code was 0x80040217. The server response was not available” etc.
To solve this issue in ASP.net we can use the Collaboration Data Objects (CDO) for Windows 2000 library (Cdosys.dll) to send an e-mail message with attachments. Microsoft Outlook use this DLL to send email. In your ASP.net solution, you have to add referance “Microsoft CDO for windows 2000 Library“. It will add two marked dll in Bin folder.
![image to add referance]()
Now do the bellow code in C#.net:
public static void SendMail(string FromName, string FromEmail, string ReceiverEmail, string CC, string BCC, string subj, string Mssg)
{
const var cdoSendUsingPort = 2;
const var cdoBasicAuth = 1;
const var cdoTimeout = 60;
var mailServer = "mail.XXXXXXX.net";
var SMTPport = 465;
var mailusername = "yyy@XXXXXXX.net";
var mailpassword = "PPPPXXXX";
var objEmail = CreateObject("CDO.Message");
var objConf = objEmail.Configuration;
var objFlds = objConf.Fields;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = cdoSendUsingPort;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/smtpserver") = mailServer;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = SMTPport;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/smtpusessl") = true;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/smtpconnectiontimeout") = cdoTimeout;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate") = cdoBasicAuth;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/sendusername") = mailusername;
objFlds.Item("http://schemas.microsoft.com/cdo/configuration/sendpassword") = mailpassword;
objFlds.Update();
objEmail.To = ReceiverEmail;
objEmail.From = FromEmail;
objEmail.CC = CC;
objEmail.BCC = BCC;
objEmail.Subject = subj;
objEmail.HTMLBody = Mssg;
objEmail.Send();
}
In VB.net
Public Shared Sub SendMail(ByVal FromName As String, ByVal FromEmail As String, ByVal ReceiverEmail As String, ByVal CC As String, ByVal BCC As String, ByVal subj As String, ByVal Mssg As String)
''#################Sending Email##########################
Const cdoSendUsingPort = 2 ' Send the message using SMTP
Const cdoBasicAuth = 1 ' Clear-text authentication
Const cdoTimeout = 60 ' Timeout for SMTP in seconds
Dim mailServer = "mail.XXXXXXX.net"
Dim SMTPport = 465
Dim mailusername = "yyy@XXXXXXX.net"
Dim mailpassword = "PPPPXXXX"
Dim objEmail = CreateObject("CDO.Message")
Dim objConf = objEmail.Configuration
Dim objFlds = objConf.Fields
With objFlds
.Item("http://schemas.microsoft.com/cdo/configuration/sendusing") = cdoSendUsingPort
.Item("http://schemas.microsoft.com/cdo/configuration/smtpserver") = mailServer
.Item("http://schemas.microsoft.com/cdo/configuration/smtpserverport") = SMTPport
.Item("http://schemas.microsoft.com/cdo/configuration/smtpusessl") = True
.Item("http://schemas.microsoft.com/cdo/configuration/smtpconnectiontimeout") = cdoTimeout
.Item("http://schemas.microsoft.com/cdo/configuration/smtpauthenticate") = cdoBasicAuth
.Item("http://schemas.microsoft.com/cdo/configuration/sendusername") = mailusername
.Item("http://schemas.microsoft.com/cdo/configuration/sendpassword") = mailpassword
.Update()
End With
objEmail.To = ReceiverEmail
objEmail.From = FromEmail
objEmail.CC = CC
objEmail.BCC = BCC
objEmail.Subject = subj
objEmail.HTMLBody = Mssg
'objEmail.AddAttachment "C:\report.pdf"
objEmail.Send()
End Sub
Referance:
Original post
Implicit & Explicit SMTP http://help.fogcreek.com/9002/using-an-smtp-server-with-ssl
use the Cdosys.dll library to send an e-mail message with attachments https://support.microsoft.com/en-us/help/310212/how-to-use-the-cdosys-dll-library-to-send-an-e-mail-message-with-attac
