Forum: Ruby on Rails Mailer failure: ArgumentError: A sender (Return-Path, Sender or From) required to send a message

I have two mailer procedures in the same app and same mailer (Rails
3.1/1.9.2). The first one fails with the message below, the second works
fine. Both these results are through irb. Anyone have an idea as to why?
Also, in my application.rb I do have: ActionMailer::Base.default :from 
=>
"WaveLineup <system@wavelineup.com>" defined.

FAILS
  def password_reset_instructions(user)
      @user = user
      @url = edit_password_reset_url(user.perishable_token)
      mail(:to => user.email, :subject => 'Password Reset for 
WaveLineup')
  end

  Error message:
  ruby-1.9.2-p290 :010 >
SystemMailer.password_reset_instructions(user).deliver
  ArgumentError: A sender (Return-Path, Sender or From) required to send 
a
message


WORKS FINE
  def wavelineup_invitation(invitation)
      @referring_user = invitation.referring_user
      @token = invitation.token
      mail(:to => invitation.email, :subject => 'Invitation to 
WaveLineup
Travel Card System for Network practitioners')
  end

What is the output when you try this:

  def password_reset_instructions(user)
      @user = user
      @url = edit_password_reset_url(user.perishable_token)
      p user
      mail(:to => user.email, :subject => 'Password Reset for
WaveLineup')
  end