When delivering a message of any kind, it pays to think of your medium. I usually refer to 'walk over if possible, call when possible, message or mail when needed' as a great working model. My main assumptions underlying this methodology are my understanding of the 'bandwidth of the medium' (adding non-verbal communication), (legal) clarity and the fact that psychological distance between sender and receiver can greatly impact the way the message is received.
Tyler Cowen of Marginal Revolution highlighted research that might add even more considerations:
"It is widely assumed that thinking is independent of language modality because an argument is either logically valid or invalid regardless of whether we read or hear it. This is taken for granted in areas such as psychology, medicine, and the law."
The researchers demonstrate that thinking from spoken information leads to more intuitive performance compared with thinking from written information.
"Consequently, we propose that people think more intuitively in the spoken modality and more analytically in the written modality."
The effect was found to be robust across both the English and Chinese language and during five separate experiments (N=1,243). An interesting comment was made by one of Tyler's readers, who asked how Plato's written dialogues might be viewed in this light. Does a conversation formed in your head from reading have the same effect as listening to that conversation?