Both my masters research and my PhD research required the use of epistolary interviews: asynchronous, one-to-one interviews that are mediated by technology.
Epistolary interviewing offers several advantages. The method allows both interviewer and respondent to select suitable interview times, provides time to consider questions and responses and eliminates the need for transcription. It has the potential to produce rich data because it produces thoughtful exchanges in which both interviewer and respondent have opportunities to consider, clarify and expand their meaning.
The epistolary nature of such interviews means that, as in a sequence of written letters, a relationship between the correspondents can be established and developed over time. The method also allows a researcher to conduct several interviews simultaneously, so data from one interview can be tested in or used to develop other interviews.