This transport extends Email::Sender::Transport::Wrapper, meaning that it
must be created with a transport attribute of another
Email::Sender::Transport. It will proxy all email sending to that transport,
but only after first deciding if it should fail.
It does this by calling each coderef in its failure_conditions attribute,
which must be an arrayref of code references. Each coderef will be called and
will be passed the Failable transport, the Email::Abstract object, the
envelope, and a reference to an array containing the rest of the arguments to
If any coderef returns a true value, the value will be used to signal failure.