Email::Abstract provides module writers with the ability to write
simple, representation-independent mail handling code. For instance, in
the cases of Mail::Thread or Mail::ListDetector, a key part of the code
involves reading the headers from a mail object. Where previously one
would either have to specify the mail class required, or to build a new
object from scratch, Email::Abstract can be used to perform certain
simple operations on an object regardless of its underlying
representation.