The following vb6 example codes demonstrate how to send email without specified SMTP server.
How does it work?
In general, we send email via specified SMTP server. How does the specified SMTP server know what address this email should be sent to? The answer is… it queries MX record of recipient’s domain via DNS lookup. It then forwards this email to the SMTP server queried from DNS server. If recipient’s server doesn’t work fine, sender’s SMTP server will send a failure-delivery report to the sender telling it failed to send out the email.
How does EASendMail SMTP component work with “Send email directly”? Firstly, it queries MX record for recipient address from DNS, then sends email to recipient’s email server directly. In short, if no SMTP server is specified in the code, EASendMail will send email to recipient directly. Since querying DNS server consumes CPU time and networking resource, the performance of “Send email directly” is lower than sending email with specified SMTP server. Moreover, nowadays more and more SMTP servers block email sent from dynamic IP address, so we don’t recommend you to use “Direct Send Email” except you have a static IP address or you encounter problem with your ISP SMTP server.
Every recipient may have different SMTP server, if there are multiple recipients in one message and you want to send email directly, you should send the email to the recipients one by one.
To implement this feature, you just need to put nothing to SMTP server address.
EASendMail is a SMTP component which supports all operations of SMTP/ESMTP protocols (RFC 821, RFC 822, RFC 2554). Before you can use the following example codes, you should download the EASendMail Installer and install it on your machine at first.
To use EASendMail SMTP ActiveX Object in your project, the first step is “Add reference
of EASendMail to your project”. Please select menu ->
EASendMailObj ActiveX Object, click
OK, the reference will be added
to current project, and you can start to use it to send email in your project.
The following example codes demonstrate sending email message using MX DNS lookup.
In order to run it correctly, please change
recipient value to yours.
To get full sample projects, please download and install EASendMail on your machine.
Private Sub btnSendMail_Click() Dim oSmtp As New EASendMailObjLib.Mail oSmtp.LicenseCode = "TryIt" ' Set your sender email address oSmtp.FromAddr = "firstname.lastname@example.org" ' Add recipient email address oSmtp.AddRecipientEx "email@example.com", 0 ' Set email subject oSmtp.Subject = "simple email from VB 6.0 project" ' Set email body oSmtp.BodyText = "this is a test email sent from VB 6.0 project, do not reply" ' Do not set SMTP server address oSmtp.ServerAddr = "" MsgBox "start to send email ..." If oSmtp.SendMail() = 0 Then MsgBox "email was sent successfully!" Else MsgBox "failed to send email with the following error:" & oSmtp.GetLastErrDescription() End If End Sub
With above code, if you get error like “5xx IP address rejected”, that means your IP address is blocked by the recipient’s SMTP server. You have to specify a SMTP server with user authentication to relay your email.
If your machine doesn’t have a static IP address, then I don’t suggest that you send email directly.
To learn more detail about EASendMail Serivce, please have a look at Work with EASendMail Service (Email Queuing).
TLS is the successor of SSL, more and more SMTP servers require
TLS 1.2 encryption now.
If your operating system is
Windows XP/Vista/Windows 7/Windows 2003/2008/2008 R2/2012/2012 R2, you need to
enable TLS 1.2 protocol in your operating system like this:
Seperate builds of run-time dll for 32 and x64 platform
|Installation Path\Lib\native\x86\EASendMailObj.dll||32 bit|
|Installation Path\Lib\native\x64\EASendMailObj.dll||64 bit|
For VB6, C++, Delphi or other standard exe application, you can distribute EASendMailObj.dll with your application to target machine without COM-registration and installer. To learn more detail, please have a look at Registration-free COM with Manifest File.
For ASP, VBScript, VBA, MS SQL Stored Procedure, you need to install EASendMail on target machine by EASendMail installer, both 32bit/x64 DLL are installed and registered.