Quote:

In addition, the origin of the diaeresis is from a small e placed over the vowel undergoing umlaut.



So I suppose this explains why sometimes you see words from German being spelled with an extra e, in a rather consistent way. For instance, you will see the surname Dörfler spelled as Doerfler, and Müller as Mueller. I've seen these two in e-mail addresses, where it would be impossible to put in diaereses. Thanks, zmjezhd!