Notification from email setting auto changed in SBE plugin

Subscribe by email plugin network setting, We filled in specific email address in 'Notification From Email' to sender's address for all outgoing notified messages, but it was automatically changed to an invalid email address (no-reply@16angelal), 16angelal is one of blog users who doesn't have admin privilege to change this setting, It directly caused outgoing messages can't be delivered due to invalid domain validated by recipient's email server, I would like to know how and why it could happen.Thanks