Be polite. It could save your reptuation.
For centuries, English letter-writers used flowery phrases such as "My dear Mister Pecksniff" and "Your most humble and obedient servant." We smile at such ingratiating phrases, versions of which are still used in some European correspondence. But did our ancestors know something we don't?
Today's e-mail evolved after the 1970s, when scientists (mostly male) messaged each other with regard to government and other research. Because males avoided typing classes, most of them approached a keyboard with two fingers. In addition, they had little need to ingratiate themselves with their correspondent. Thus arose both smilies and the cryptic style that the rest of us imitated.
But all written messages arrive stripped of tone, gesture, timing, and interactivity. The message may have been written in haste and constitute the utilitarian minimum of denotation. I propose (I have no proof) that readers see an e-mail as a sort of verbal inkblot. On this minimal stimulus, the reader imposes an often unconscious "spin." Thus the reader may read offense where none was intended. (The famous case of the all-capital "screamed" message is only one instance.)
Equally problematic in business, the writer may use the minimal stimulus of email to convey intended insult and then deny it.
In short, e-mail is a minefield. You may not be Bob's most obedient servant; but an extra "thank you" or "what do you think?" can protect you from unintentional harm.
