Email from your Site

Both CalMail and bMail may block email messages originating from sites hosted on Pantheon. This is because Pantheon does not run a mail server, instead using a free SMTP service. CalMail and bMail will mark it as spam and block it even before it reaches the recipient's spam folder. Other mail providers may accept it.

If you need your site to send email to email addresses, install and configure the SMTP module.