(C#) Send Email without Mail Server

How to send an email without a mail server (so-to-speak).

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// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Is it really possible to send email without connecting to
// a mail server?  Not really.

// When people ask 'Do you support sending email without 
// a mail server'?  what they're really asking is: 'I don't
// have an SMTP server, and I want to send email.  I see
// other components available where it's not necessary
// to specify an SMTP server.  Does your component have that
// ability?'  In short, the answer is Yes.  But you need
// to understand some things before you jump in...

// Here's what happens inside those other components
// that claim to not need a mail server:  The component does
// a DNS MX lookup using the intended recipient's email address
// to find the mail server (i.e. SMTP server) for that
// domain.  It then connects to that server and delivers the
// email.  You're still connecting to an SMTP server -- just
// not YOUR server.

// Chilkat provides an MxLookup method where you can lookup
// the SMTP hostname that services any given email address. 
// You would then assign the SmtpHost property to this value.
// Chilkat can then connect directly to the recipient's mail 
// server and deliver the email.

// There are a few gotcha's though...

// First, if you're writing an application that is widely 
// distributed, your app might be running within a network
// that blocks outgoing connections to the SMTP port.
// Earthlink, for example, is one major ISP that does this.
// When you are connected to the Internet via Earthlink,
// your apps can *only* connect to Earthlink's SMTP server
// and will not be able to reach any remote servers.  To send
// email, you must use Earthlink's SMTP as a relay.  This is
// common with ISPs.  So... if your application is coded
// as in this example, it will not work within those networks.
// 
// Second, some SMTP servers will reject unauthenticated
// sessions attempting to send email from dynamic IP addresses.
// You may see this error in your LastErrorText:
// 553-Your attempt to send email to us has been blocked
// 553-because your email server is not currently on that domain's Accepted
// 553-Senders list. To request addition to their Accepted Senders list,
// 553-please navigate with a Web browser to the following URL:
// 553-http://reportrbl.gate2service.com/Whitelist/?IPAddress=67.173.123.150
// 553 See http://www.dnsbl.us.sorbs.net/ (dul)

// In a nutshell, just because you were able to do the MxLookup
// and connect to the recipient's mail server, doesn't mean
// you'll be able to send email -- it depends on the IP address
// from which you're connecting.

// Finally, the DNS lookup is potentially time consuming.
// In addition, you cannot use somebody else's email server
// as a relay, so if you're connecting to smtp.xyz.com, you
// can only send email to email addresses at xyz.com.
// To send email to 3 recipients at different domains means
// making 3 separate connections to 3 separate SMTP servers
// to send the email one at a time.

// The mailman object is used for sending and receiving email.
Chilkat.MailMan mailman = new Chilkat.MailMan();

string recipient = "admin@chilkatsoft.com";

// Do a DNS MX lookup for the recipient's mail server.
string smtpHostname;
smtpHostname = mailman.MxLookup(recipient);
if (mailman.LastMethodSuccess != true) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

Debug.WriteLine(smtpHostname);

// Set the SMTP server.
mailman.SmtpHost = smtpHostname;

// Create a new email object
Chilkat.Email email = new Chilkat.Email();

email.Subject = "This is a test";
email.Body = "This is a test";
email.From = "My Name <myname@mydomain.com>";
email.AddTo("",recipient);

bool success = mailman.SendEmail(email);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
}
else {
    Debug.WriteLine("Mail Sent!");
}