Did you ever try sending out a mail on a application installed on a localhost, but the mail will not be delivered because it requires a SMTP and on localhost this can be a tough thing to setup, but with Papercut you can test sending mails from your application.

Papercut is a simplified SMTP server designed to only receive mails, (note : you cannot sends mail from it, only receive it).You can also see the received mail from the application and you can also minimize it to the system tray and it keeps monitoring for any mails in the background.

It requires no installation, but works on Windows OS with .NET Framework v3.5 installed.

Download Papercut Local SMTP