Email Sending

Introduction

Sending emails is a very common task for most applications. ASP.NET Boilerplate provides the basic infrastructure to send emails in a simple way. It also separates the email server configuration from the sending of emails.

IEmailSender

IEmailSender is a service to send emails without knowing the details. Example usage:

public class TaskManager : IDomainService
{
    private readonly IEmailSender _emailSender;

    public TaskManager(IEmailSender emailSender)
    {
        _emailSender = emailSender;
    }

    public void Assign(Task task, Person person)
    {
        //Assign task to the person
        task.AssignedTo = person;

        //Send a notification email
        _emailSender.Send(
            to: person.EmailAddress,
            subject: "You have a new task!",
            body: $"A new task is assigned for you: <b>{task.Title}</b>",
            isBodyHtml: true
        );
    }
}

We simply injected IEmailSender and used the Send method. The Send method has additional overloads. For example, it can also get a MailMessage object (not available for .NET Core since .NET Core does not include SmtpClient and MailMessage).

ISmtpEmailSender

There is also an ISmtpEmailSender which extends IEmailSender and adds a BuildClient method to create an SmtpClient and then directly uses it (not available for .NET Core since .NET Core does not include SmtpClient and MailMessage). Using IEmailSender will be enough for most cases.

NullEmailSender

There is also a null object pattern implementation of IEmailSender, aptly named NullEmailSender. You can use it in unit tests or inject IEmailSender with the property injection pattern.

Configuration

Email Sender uses a settings management system to read email-sending configurations. All the setting names are defined in the Abp.Net.Mail.EmailSettingNames class as constant strings.

Their values and descriptions:

• Abp.Net.Mail.DefaultFromAddress: Used as the sender's email address when you don't specify a sender when sending emails (just like in the example above).
• Abp.Net.Mail.DefaultFromDisplayName: Used as the sender's display name when you don't specify a sender when sending emails (just like in the example above).
• Abp.Net.Mail.Smtp.Host: The IP/Domain of the SMTP server (default: 127.0.0.1).
• Abp.Net.Mail.Smtp.Port: The Port of the SMTP server (default: 25).
• Abp.Net.Mail.Smtp.UserName: Username, if the SMTP server requires authentication.
• Abp.Net.Mail.Smtp.Password: Password, if the SMTP server requires authentication.
• Abp.Net.Mail.Smtp.Domain: Domain for the username, if the SMTP server requires authentication.
• Abp.Net.Mail.Smtp.EnableSsl: A value that indicates if the SMTP server uses SSL or not ("true" or "false". Default: "false").
• Abp.Net.Mail.Smtp.UseDefaultCredentials: If true, uses default credentials instead of the provided username and password ("true" or "false". Default: "true").

MailKit Integration

Since .NET Core does not support the standard System.Net.Mail.SmtpClient, we need a 3rd-party vendor to send emails. Fortunately, MailKit provides a good replacement for the default SmtpClient. It's also suggested by Microsoft.

The Abp.MailKit package gracefully integrates in to ABP's email sending system, so you can still use IEmailSender as described above to send emails via MailKit.

Installation

First, install the Abp.MailKit NuGet package to your project:

Install-Package Abp.MailKit

Integration

Add the AbpMailKitModule to the dependencies of your module:

[DependsOn(typeof(AbpMailKitModule))]
public class MyProjectModule : AbpModule
{
    //...
}

Usage

You can use IEmailSender as described above since the Abp.MailKit package registers the MailKit implementation for it. It also uses the same configuration.

Customization

You may need to make additional configuration or customizations while creating MailKit's SmtpClient. In that case, you can replace the IMailKitSmtpBuilder interface with your own implementation. You can derive from the DefaultMailKitSmtpBuilder to make it easier. For instance, you may want to accept all SSL certificates. In that case, you can override the ConfigureClient method as shown below:

public class MyMailKitSmtpBuilder : DefaultMailKitSmtpBuilder
{
    public MyMailKitSmtpBuilder(ISmtpEmailSenderConfiguration smtpEmailSenderConfiguration) 
        : base(smtpEmailSenderConfiguration)
    {
    }

    protected override void ConfigureClient(SmtpClient client)
    {
        client.ServerCertificateValidationCallback = (sender, certificate, chain, errors) => true;

        base.ConfigureClient(client);
    }
}

You can then replace the IMailKitSmtpBuilder interface with your implementation in the PreInitialize method of your module:

[DependsOn(typeof(AbpMailKitModule))]
public class MyProjectModule : AbpModule
{
    public override void PreInitialize()
    {
        Configuration.ReplaceService<IMailKitSmtpBuilder, MyMailKitSmtpBuilder>();
    }

    //...
}

(Don't forget to add the "using Abp.Configuration.Startup;" statement since the ReplaceService extension method is defined in that namespace)