Being in any kind of profession that involves a seller-buyer interaction chain, mails rank as the most professional and personalized form of communication.

Now figure this situation. Your are at the toe's end of cracking a important business deal. Your boss/manager wants you to dig for the client details from months back. If you are one of those who is a little unorganized or never does the regular cleaning up activity, finding that one mail is going to seem like a gargantuan task.

So what happens in such a situation is you end up mentally anlayzing a situation in a bloated parameter. Mess up in work follows.

This in short is what makes up a perfect email anxiety situation. More than physical, it is a psychological condition.