In Spree 3.0 "Mail Method Settings" not available by default.
Rails version 4.2.0
Using "gem 'spree_mail_settings', github: 'spree-contrib/spree_mail_settings', branch: '3-0-stable'" in admin panel one link generate in Configuration menu "Mail Method settings".
All configuration done. But when Click on "Test Mail" Button it gives error "An SMTP From address is required to send a message. Set the message smtp_envelope_from, return_path, sender, or from address."