Not my thoughts. I always use "dis".
The Green Book Authority says
"
The word comes into English in the early 1500s from Italian
dispacciare, 'to send off with speed', although there were forms of the word in Spanish and Portuguese with
des-.
The
dis- spelling was the norm in English until Dr Johnson wrote his dictionary in 1755 and included the word as
despatch. Since he himself used
dispatch in his own writing and since all his sources that he used for the dictionary had the form
dispatch, the theory is that this was a typographical error. From that moment on English has wavered over the correct spelling of this word."
To dispatch or to despatch - that was the question from a dictionary user who had been taught at school that despatch was correct and dispatch was incorrect. Read more...
www.macquariedictionary.com.au