If the user has a list of e-mail addresses and needs to hash them, the results will be different depending on whether the e-mail address is written as lowercase or uppercase. Give the user the choice to make all addresses uppercase, or lowercase, or just hash them as they are supplied.
Thinking about it, this just complicates matters. Entry added to user manual instead to advise users that they should prepare their lists of text before running through quickhash. Closed.