Rails 3 ActionMailer error-el nombre de host no coincidía con el certificado del servidor

Estoy configurando SMTP para mi aplicación Rails 3.

Esta configuración funciona.

ActionMailer::Base.delivery_method = :smtp
ActionMailer::Base.smtp_settings = {  
  :address              => "smtp.gmail.com",  
  :port                 => 587,  
  :domain               => "mydomain.com",  
  :user_name            => "<username>",  
  :password             => "<password>",  
  :authentication       => "plain",  
  :enable_starttls_auto => true  
}

Pero esta configuración no. Da"hostname was not match with the server certificate"

ActionMailer::Base.delivery_method = :smtp
ActionMailer::Base.smtp_settings = {  
  :address              => "some_other_server.com",  
  :port                 => 587,  
  :domain               => "mydomain.com",  
  :user_name            => "<username>",  
  :password             => "<password>",  
  :authentication       => "plain",  
  :enable_starttls_auto => true  
}

Extrañamente, la misma configuración funciona en Rails 2.3.8. (: tls => true)

¿Qué pasa?