Test sending emails while developing

I frequently have to send emails from web applications. But before I deploy to a production environment, I want to make sure the mechanism works and the right mails are constructed. Here’s two ways to do that.

Monkey patching the Zope MailHost

When developing a Zope based application, the Products.PrintingMailHost package can really help you out. By including this package in your setup, the Zope MailHost class is patched so no actual emails are sent. Instead the content of email is printed to the standard output.

SMTP server

But when working on a Django application (or any other non Zope project) there is no MailHost class that can be monkey patched. Python’s smtpd module to the rescue. The first step is to configure the application to use localhost as the SMTP server on a random port (say: 1025). Next, go to the command line and type:

$ python -m smtpd -n -c DebuggingServer localhost:1025

Just like the PrintingMailHost, this SMTP server prints the emails to standard output. For more information see the “Testing e-mail sending” section in the Django documentation.

Update 2010-08-09

For the developer with a deadline: install django-extensions which has a couple of usefull extra features. One of them is the mail_debug management command. This commands starts the same SMTP debugging server, but you don’t have to remember the right incantation.

HTTP server

Somewhat related to this: if you want to test your application against an HTTP server, you can use this command:

$ python -m SimpleHTTPServer

The SimpleHTTPServer module can be used to get server up-and-running quickly. It can also be a simple way to, for instance, copy files from one machine to another. By running the HTTP server in the directory containing the files, you can access the files via your browser on another machine. Safe? No. Convenient? Yes.