Смотри: /redmine/app/models/mailer.rb
Например, Уведомления о новой задаче:
# Builds a mail for notifying to_users and cc_users about a new issue
def issue_add(issue, to_users, cc_users)
redmine_headers 'Project' => issue.project.identifier,
'Issue-Id' => issue.id,
'Issue-Author' => issue.author.login
redmine_headers 'Issue-Assignee' => issue.assigned_to.login if issue.assigned_to
message_id issue
references issue
@author = issue.author
@issue = issue
@users = to_users + cc_users
@issue_url = url_for(:controller => 'issues', :action => 'show', :id => issue)
mail :to => to_users.map(&:mail),
:cc => cc_users.map(&:mail),
:subject => "[#{issue.project.name} - #{issue.tracker.name} ##{issue.id}] (#{issue.status.name}) #{issue.subject}"
end