Introduction
Email serves as a ubiquitous, asynchronous notification and information distribution system. Not surprisingly, there are many
web development scenarios where server-side code needs to generate an email and scuttle it off to the intended recipient.
The email may be destined for a user of the website, informing them of their newly created user account, reminding them of
their forgotten password, or emailing them an invoice. Or it may be destined for a web developer or site administrator, providing
information of an unhandled exception that just transpired or user feedback.
Fortunately, ASP.NET makes sending email a breeze. The .NET Framework version 1.x included a number of classes in the
System.Web.Mail class that allowed programmatically sending an email with a few scant lines of code.
While this namespace and these classes still exist in the .NET Framework version 2.0, they have been deprecated in favor
of new mail-related classes found in the System.Net.Mail
namespace. (For an article on sending email in ASP.NET version 1.x, see Sending
Email from an ASP.NET 1.x Web Page or consult www.SystemWebMail.com.)
In this article we'll look at the classes in the System.Net.Mail namespace and see how to send an email from
an ASP.NET 2.0 page's code-behind class. We'll also look at specifying relay server information in Web.config and
how this information can be used in some of the built-in ASP.NET server controls for sending emails (such as when a user creates
an account or needs a password reminder/reset). Read on to learn more!
Exploring the Classes in the System.Net.Mail Namespace
There are 16 different classes in the System.Net.Mail namespace, all related to send email to a specified
Simple Mail Transfer Protocol (SMTP) server for delivery. The two core classes
in this namespace are:
MailMessage -
represents an email message; has properties like From, To, Subject, Body,
and so on.
SmtpClient -
sends a specified MailMessage instance to a specified SMTP server.
When sending an email from an ASP.NET 2.0 page you will, typically:
Create a MailMessage object
Assign its properties
Create an instance of the SmtpClient class
Specify details about the SMTP server to use (if they're not already specified within Web.config)
Send the MailMessage via the SmtpClient object's Send method
Steps 1 and 2 may be bypassed as the SmtpClient class's Send method can accept either
a MailMessage object or four strings, representing the from, to, subject, and body contents of the email message.
The System.Net.Mail namespace's other classes allow for more advanced email functionality. There are classes
that can be used to add attachments to an email message, to embed objects within an email, to specify SMTP server authentication
information, and Exception-derived classes for handling SMTP-specific exceptions. We'll examine using some of
these other classes for more advanced scenarios in future articles.
Providing the SMTP Server's Details
When sending an email to a friend from Outlook or GMail, the email program establishes a connection with a relay
server and sends the contents of the email message, along with information such as the date the email was composed, the email body's
format (text or HTML, for example), the recipient(s), and so on. The relay server accepts the message and then
connects to the recipient's SMTP server and sends the message. Once the message has been delivered, the recipient can, at some later
point in time, pull down the message using a different protocol (such as IMAP
or POP3).
Therefore, to send an email from an ASP.NET page we need to provide the SmtpClient class with information about
the relay server. Along with the hostname of the relay server, you can specify the port (typically port 25 is used),
whether or not to use SSL when communicating your email message contents to the relay server, and authentication
credentials (if necessary). Alternatively, if you have a local SMTP service installed on your web server, it may periodically
monitor a particular "drop-off" directory, sending any messages that appear in that directory. You can configure whether
the SmtpClient class relays its email messages to a separate relay server or if it drops it off in a specified
pickup directory through the DeliveryMethod property.
The relay server information used by the SmtpClient class can be specified programmatically, through the
SmtpClient class's properties, or can be centralized in Web.config. To use the Web.config
approach, add a <system.net> element within the <configuration> element. Then, add
a <mailSettings> element that contains
an <smtp> element whose settings are
specified within its <network> child element, like so:
<configuration>
<!-- Add the email settings to the <system.net> element -->
<system.net>
<mailSettings>
<smtp>
<network
host="relayServerHostname"
port="portNumber"
userName="username"
password="password" />
</smtp>
</mailSettings>
</system.net>
<system.web>
...
</system.web>
</configuration>
The host attribute contains the relayServerHostname. If you are using an external relay server, the relayServerHostname
might be something like smtp.yourisp.com. If the relay server's port number is something other than the typical
port 25, specify it through the port attribute. Most external relay servers require authentication of some sort
(in order to prevent anonymous spammers from sending their garbage through the relay). The userName and password
attributes can be provided in the case where username/password authentication is needed.
Only a subset of the SmtpClient properties can be specified through settings in Web.config. To
customize the other SmtpClient properties - EnableSsl, Timeout, and so on - set them
programmatically when sending the email (step 4 from the list of five steps examined earlier in this article).
Sending an Administrator Email Through a Feedback Web Page
To illustrate sending an email using the MailMessage and SmtpClient classes, I've created a simple
feedback page example. In this page the user is prompted for their email address, the subject of their feedback, and their
feedback.
Once the user has supplied the feedback information and clicked the "Send Feedback" button, a postback ensues and the
Button's Click event fires. Inside the event handler, a MailMessage object is created and its To,
From, Subject, and Body properties are set according to the information provided by
the user. With the MailMessage object created and its properties populated, the email is then sent through
the SmtpClient class's Send method.
Protected Sub SendEmail_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles SendEmail.Click
'!!! UPDATE THIS VALUE TO YOUR EMAIL ADDRESS
Const ToAddress As String = "you@youremail.com"
'(1) Create the MailMessage instance
Dim mm As New MailMessage(UsersEmail.Text, ToAddress)
'(3) Create the SmtpClient object
Dim smtp As New SmtpClient
'(4) Send the MailMessage (will use the Web.config settings)
smtp.Send(mm)
End Sub
We didn't need to set any of the SmtpClient class's properties here in code because they have been specified
in Web.config (download the complete code at the end of this article to run this application on your computer).
Conclusion
Along with a plethora of other improvements from ASP.NET 1.x, the email sending capabilities in ASP.NET 2.0 have been updated
and moved to a new namespace, System.Net.Mail. In 2.0 the relay server settings can easily be decoupled from the
ASP.NET code and moved into the Web.config file, as we saw in this example. Moreover, there's better support for
relay server authentication. Future articles will explore more advanced email scenarios, such as: crafting HTML-formatted emails,
sending attachments, embedding objects within the email body, handling SMTP/relay server-related exceptions, and so on.
