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 berkeley.edu email addresses, install and configure the SMTP module.
If you use the Drupal SMTP module or change the configuration of UCB SMTP, do not use a personal email address - bMail, Gmail, or other. Your email password or your CalNet passphrase will be at risk.