The idea for MockSMTP emerged to solve a recurrent problem encountered when developing web apps here at Xilinus:
finding a quick way to test e-mails sent by applications.
Each existing option has its own niggles.
You can use an actual SMTP server – that of your SMTP provider or Google SMTP, for instance.
But this requires an internet connection, and configuration can be problematic.
What is more, once the e-mail has been sent, you have to check your own e-mail client to read it, and your mail can take time to get there.
The best that can be said for this solution is that it shows you the actual rendering in your email client - great when you want to check how your mail looks in HTML format.
Alternatively, you can run a local SMTP server such as postfix, but the same drawbacks apply. Sometimes your mail gets caught by spam filters and never turns up at all.
Yet another option is to run a dummy local SMTP server. This doesn't require an internet connection and there's no delay in reading your mail.
But in most cases, you'll be looking at the mail in a console app. Reading raw HTML isn't easy - and you can't check what the HTML rendering looks like.
We decided to improve on all this by developing MockSMTP.
We use it almost everyday now and we are really happy with it.