If you have 2-factor authentication enabled in your iCloud account, you'll need to generate an app-specific password for setting up SMTP in your ISN!
Setting this up is quick and easy!
Log into your iCloud account here:
Navigate to the section labeled Security and click the Generate Password button.
Name the password something like ISN and click Create
On the next screen you'll be given an app-specific password! Copy that password, and paste it into the 'Password' field in your ISN under Settings -- SMTP Settings in the record for your iCloud account.
If you don't have an iCloud account set up, click Add SMTP Setting
In the pop-up box add the following information:
Email Address: your full @me.com Email Address (including @me.com) (Example: YourUsername@me.com)
Username: your_email_account_username (Example: YourUsername@me.com)
Password: Your email account password (Password you use to login into your email account.)
Check the box that says, This SMTP server requires TLS