Here is a sample that uses the live.com freemailer (formally called Hotmail) which does require a secure connection.
PS> Send-MailMessage -Body 'My mail message can contain special characters: äöüß' -From email@example.com ` -to firstname.lastname@example.org -Credential email@example.com -SmtpServer smtp.live.com ` -Subject 'Sending Mail from PowerShell' -Encoding UTF8 -UseSsl
Note that PowerShell v3
Send-MailMessage accepts UTF8 directly so you no longer need to submit the awkward (
There are plenty of websites that list SMTP server URLs for your favorite provider: http://www.e-eeasy.com/SMTPServerList.aspx.