Redmine

Hello folks,
I configured email notification in my configuration.yml file.
I´m using an Exchange 2010 as mail server, and tried several configurations for that.

But every time, when I like to send a test mail I got the following error:
"An error occurred while sending mail (undefined method `new' for "smtp":String)"

I´m using Redmine 2.1.0 and my mail settings in the configuration.yml looks like:

production:
email_delivery:
delivery_method: smtp
smtp_settings:
tls: true
enable_starttls_auto: true
address: '<my smtp server address>'
port: 25
domain: '<my domain>' # 'your.domain.com' for GoogleApps
authentication: :login
user_name: '<my smtp user>'
password: '<my smtp passwd>'
openssl_verify_mode: 'none'

Why doesn´t work that?

greetings