Following on to my short rant yesterday, I wanted to share some information from a survey we did about a year ago. We surveyed ~1400 people about their email management habits, how overloaded they felt, if they used conversation views, folders, filters/rules, sorting, etc as well as asking them to self-report on how much mail they receive/send/have filtered by rules/etc per day.
We tried very hard to find some something different in the behaviors of the people who felt overloaded vs those who didn't - e.g. surely people who get a lot of email are more likely to feel overloaded, right? Or surely people who take advantage of management features like rules and conversation view feel more on top of things than those who don't?
The answer: Nope. No correlation. From the report written by a researcher on my team: "Crosstabs and frequencies analyses indicate that perceived effectiveness at mail management does not relate to use of Outlook/OWA features (Sorting, Search Folders, etc.), to types of mail received (messages sent by coworkers, thread-related messages, etc.), or to use of Outook/OWA views (primary view, secondary view, level of Conversation View experience)."
Here are the answers for how overwhelmed people felt, one chart for those who worked at microsoft and another for those who didn't:
Another quote: "Factors relating to volume of mail are not as strongly related to mail management effectiveness as might be expected. The strongest “volume” factor is “daily time spent managing mail”: 74% of respondents who find mail management difficult, as compared to only 58% of respondents who manage mail effectively, spend more than 2 hours per day scanning, reading, composing, and organizing mail."
Of course all self-reported data (# of hours spent managing mail, # of messages received) is not necessarily accurate but the lack of correlation between these users' perceptions of their overload and their usage of mail management techniques is very interesting. We also kept the ranges quite broad, for example when we asked about messages received per day the options were spaced as follows: 0-50, 51-100, 101-300, 300+.
 Note that the participants were heavily tilted towards a more technical audience - half internal microsoft, half external but the external folks tended to work heavily with software/technology in some way.