Sunday, October 9, 2011

Send mail From Asp.Net

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!

After reading this article, be sure to check out Sending Email in ASP.NET 2.0: HTML-Formatted Emails, Attachments, and Gracefully Handling SMTP Exceptions, where we'll look at sending HTML-formatted emails, emails with attachments, and gracefully handling SMTP exceptions! Then mosey over to Sending Email in ASP.NET 2.0: Reply-To, Priority, and Read Receipts for even more great email content.

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:
  1. Create a MailMessage object
  2. Assign its properties
  3. Create an instance of the SmtpClient class
  4. Specify details about the SMTP server to use (if they're not already specified within Web.config)
  5. 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.
<table border="0">
    <tr>
        <td><b>Your Email:</b></td>
        <td><asp:TextBox runat="server" ID="UsersEmail" Columns="30"></asp:TextBox></td>
    </tr>
    <tr>
        <td><b>Subject:</b></td>
        <td><asp:TextBox runat="server" ID="Subject" Columns="30"></asp:TextBox></td>
    </tr>
    <tr>
        <td colspan="2">
            <b>Body:</b><br />
            <asp:TextBox runat="server" ID="Body" TextMode="MultiLine" Columns="55" Rows="10"></asp:TextBox>
        </td>
    </tr>
    <tr>
        <td colspan="2" align="center">
            <asp:Button runat="server" ID="SendEmail" Text="Send Feedback" />
        </td>
    </tr>
</table>



The feedback form.
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)

    '(2) Assign the MailMessage's properties
    mm.Subject = Subject.Text
    mm.Body = Body.Text
    mm.IsBodyHtml = False

    '(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).


The received email.

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.