Redmine

I am getting error when creating/updating the issue after configuring the email. please find the log below. We would appreciate your help on this.

Started POST "/projects/horizon/issues" for 192.168.1.1 at 2013-12-22 16:50:09 +0400
Processing by IssuesController#create as HTML
Parameters: {"utf8"=>"✓", "authenticity_token"=>"UYuZBaBvnq1fv9BbwWHdwwlO2s5Cpx89Y+FRbSCh28Q=", "issue"=>{"tracker_id"=>"1", "subject"=>"Test Email configuration", "description"=>"Test Email configuration 3", "status_id"=>"1", "priority_id"=>"2", "assigned_to_id"=>"3", "parent_issue_id"=>"", "start_date"=>"2013-12-22", "due_date"=>"", "estimated_hours"=>"", "done_ratio"=>"0"}, "commit"=>"Create", "project_id"=>"horizon"}
Current user: arun (id=3)
Completed 500 Internal Server Error in 106.3ms

TypeError (can't convert nil into Hash):
app/models/mailer.rb:409:in `mail'
app/models/mailer.rb:44:in `issue_add'
app/models/mailer.rb:422:in `initialize'
app/models/mailer.rb:445:in `method_missing'
app/models/mailer.rb:52:in `block in deliver_issue_add'
app/models/issue.rb:821:in `each_notification'
app/models/mailer.rb:51:in `deliver_issue_add'

app/models/issue.rb:1514:in `send_notification'
app/models/issue.rb:163:in `create_or_update'
app/controllers/issues_controller.rb:146:in `create'