Tag Archives: SMTP

Using Amazon SES for .Net Application Mail Delivery

Until March 2012 Amazon’s Simple Email Service (SES) had limited support for mail being sent via existing .Net code and the IIS SMTP virtual server.  Some recent changes mean this is now possible so in this post I’ll quickly cover how you can configure your existing apps to utilise SES.

If you don’t understand why you should be using SES for your applications then you should be looking at the Amazon SES FAQ and before you start any of this configuration you need to ensure that you have created your SMTP credentials on the AWS console and that you have an appropriately validated sender address (or addresses).  Amazon is really strict here as they don’t want to get blacklisted for being a spammer host.

IIS Virtual SMTP Server

Firstly, let’s look at how we can setup the SMTP server as a smart host that forwards mail on to SES for you.  This approach means that you can configure all your applications to forward via IIS rather than talking directly to the SES SMTP interface.

1. Open up the IIS 6 Manager and select the SMTP Virtual Server you want to configure.

1.iis_virtual_smtp

2. Right-click on the server and select Properties.

3. In the Properties Window click on the Delivery tab.

4. On the Delivery tab click on the Outbound Security button on the bottom right.

5. In the Outbound Security dialog select “Basic Authentication” and enter your AWS SES Credentials.  Make sure you check the “TLS Encryption” box at the bottom left of the dialog.  Click OK. Your screen should look similar to this:

2.delivery_setup

6. Now open the Advanced Delivery dialog by clicking on the button.

7. Modify the dialog so it looks similar to the below.  I put the internal DNS name for my host here – the problem with this is that if you shut off your Instance the name will change and you need to update this.  Click OK.

3.advanced_delivery

Now you should be ready to use this IIS SMTP Virtual Server as a relay for you applications to SES.  Make sure you set AWS SecurityGroups up correctly and that you are restricting which hosts can relay via your SMTP server.

Directly from .Net Code

Without utilising the Amazon AWS SDK for .Net you can also continue to send mail the way you always have – you will need to make the following change to your App.config or Web.config file.

<mailSettings>
      <smtp deliveryMethod="Network" from="validated@yourdomain.com">
          <network defaultCredentials="false"
                   enableSsl="true"
                   host="email-smtp.us-east-1.amazonaws.com"
                   port="25"
                   userName="xxxxxxxx"
                   password="xxxxxxxx" />
      </smtp>
</mailSettings>

Thanks to the author of the March 11, 2012 post on this thread on the AWS support forums for the configuration file edits above.

With these two changes most “legacy” .Net applications should be able to utilise Amazon’s SES service for mail delivery.  Happy e-mailing!

Safely Testing .Net Code That Does Email Delivery

As a .Net developer you will most likely have come across the need to create and send an SMTP (email) message as part of a solution you’ve built.  When under development you will have either stubbed out the mail delivery code or will have substituted a test email address for those of the final recipients in a live environment (did your mailbox get full?!).

This approach is simple and works pretty well under development, but you know one day someone will come to you with a production problem relating to mail delivery to multiple recipients with each receiving their own copy of the message.  How do you test this without needing multiple test mailboxes and without spamming the real recipients?

A few years back I learnt of a way to test mail delivery with real email addresses that can be performed locally of a development machine with minimal risk (note I didn’t say “no risk”) that email will actually be delivered to the intended recipients.  The great thing is you don’t need to understand a lot about networking or being a sysadmin god to get this working.

IIS To The Rescue

Yes, IIS.

In this case you don’t even need any third party software – just the web application server that most ASP.Net developers know (“and love” is probably pushing the relationship a little though I think).

First off, you will need to install the SMTP feature support for IIS on your local machine.  You can get instructions for IIS 7 from TechNet as well as for IIS 6.  If you’re on IIS Express, you’re out of luck – it only supports HTTP and HTTPS.

Once you have the SMTP Feature installed you will need to make one important change – set the SMTP server to use a drop folder.  The IIS SMTP process will simply drop files into a location you’ve selected and there they will sit – each file containing an emaill message.

To make this change open the IIS Manager and select the main server node.  You should see (screenshot below) an option for SMTP E-mail.

IIS Manager with SMTP Email option highlighted

IIS Manager with SMTP Email Option Highlighted.

Double-click the SMTP E-mail option to open the settings dialog. Notice at the bottom the option labelled Store e-mail in pickup directory – you should select this and then select an appropriate location on disk.

SMTP Email Settings Page with Drop Folder Highlighted

SMTP Email Settings Page with Drop Folder Highlighted.

Right, that’s the hard bit done.

Run Teh Codez

Now you have a safe place for your test mail to sit you need to ensure that your code is configured to attempt delivery via the SMTP instance you just configured.  You can most likely achieve this by changing your application’s settings (they’re in an XML config file, right?) so that you use either of “localhost” or “127.0.0.1″ as the SMTP host name – you won’t need to change the port from the standard port 25.

Now when you run your code you should find that the mail delivery folder you set will be populated with a range of files consisting of a GUID with a .EML extension – each of these is an individual email awaiting your eager eyes.

Lovely EML Files Ready To View.

Lovely EML Files Ready To View.

The files are plain text so can be opened using Notepad or your favourite equivalent – you can view all the SMTP headers as well as the message body.  For extra goodness you can also open these files in Outlook Express (does anyone even use that any more?!) or Outlook as shown below.

Outlook Goodness - See HTML Email Body Content Easily.

Outlook Goodness – See HTML Email Body Content Easily.

I used this approach just recently to help debug some problems for a customer and I could do it using their real email addresses safe in the knowledge that I would not end up spamming them with junk test emails.

Hope you find this approach useful.

Update

I had a reader pass on a service link to Mailtrap which might be more useful if you’re looking to test with a large diverse team.