class Mail::Sendmail

def shellquote(address)

- Allows '~' as it is not unescaped in double quotes
- Allows '+' to accept email addresses with them
- Wraps in double quotes

with the following modifications:
The following is an adaptation of ruby 1.9.2's shellwords.rb file, 
def shellquote(address)
  # Process as a single byte sequence because not all shell
  # implementations are multibyte aware.
  #
  # A LF cannot be escaped with a backslash because a backslash + LF
  # combo is regarded as line continuation and simply ignored. Strip it.
  escaped = address.gsub(/([^A-Za-z0-9_\s\+\-.,:\/@~])/n, "\\\\\\1").gsub("\n", '')
  %("#{escaped}")
end