Redmine

I'd recommend checking your mail server logs.

In our setup, we use a local Postfix instance that relays all mail to a central set that we manage. This local instance provides temporary caching in case a remote relay is unavailable and is worth it just for the logging info available for troubleshooting.

I believe that the /var/log/mail.log file is standard on an Ubuntu system (I can't recall whether I setup ours custom or if it is a stock location).

Take a look at your config/configuration.yml file to see how you've configured your mail handling.

Example path: /opt/redmine/config/configuration.yml

Example settings:

# default configuration options for all environments
default:

  # Outgoing emails configuration

  # http://www.redmine.org/projects/redmine/wiki/EmailConfiguration
  # See the examples below and the Rails guide for more configuration options:
  # http://guides.rubyonrails.org/action_mailer_basics.html#action-mailer-configuration
  email_delivery:
    delivery_method: :smtp
    smtp_settings:
      address: 127.0.0.1
      port: 25

  # Configuration of SCM executable command.
  # Absolute path (e.g. /usr/local/bin/hg) or command name (e.g. hg.exe, bzr.exe)
  scm_subversion_command:  /usr/bin/svn

  # Absolute path (e.g. /usr/bin/convert, c:/im/convert.exe) to
  # the ImageMagick's `convert` binary. Used to generate attachment thumbnails.
  imagemagick_convert_command: /usr/bin/convert

# specific configuration options for production environment
# that overrides the default ones
production:

# specific configuration options for development environment
# that overrides the default ones
development: