Analyzing archives

I read a lot of email.

Ok, technically, I analyze a lot of email. One of the services that we perform for our customers is an email audit.

Follow the link for some statistics on archive volumes under typical usage patterns.

The number of messages sent and received varies widely-- the average user sends between 147 and 198 emails per month and receives between 145 and 185 emails per month.

By direction, 70% is internal, and the remaining 30% is pretty evenly split between inbound and outbound mail.

Roughly 25% of email is non-business (i.e. spam that made it past the filter, private communication, external newsletters, etc.).

Most companies have an average email size of 50-60KB. There are two reasons for this:

1) HTML/RTF email cause small messages (that could have been 1KB) to be much larger (3-10x). This drives up the baseline.
2) You may have noticed this: there are a couple of Office documents floating around your email network.

Point 2) bears further consideration: 30-50% of the email (by volume) in a typical organization is Office documents (in which I include PDF files).

This causes the following storage analysis:

1000 users * 300 emails per month * 12 months * 60KB = annual storage burden of 206 GB, on average, per thousand users. That would be 2 TB per 10,000 users (per year).

Your mileage may vary, of course.