We’ve all been there – you try to send an email from your work computer and a message flashes up saying your inbox is so full nothing can be sent. So you delete a couple of messages to get back within limit and carry on until the next time. According to workplace communications consultancy Expert Messaging, office workers have an average of 450 emails in their inbox, but those with generous IT departments are stashing up to 3,000.

Imagine if you had a real life in-tray with that many messages in it. Unless you tame your inbox it can become a sprawling, suffocating beast that will squeeze the life and efficiency out of you. So don't delay – take charge today.

Clearing your inbox is easier than you think. In fact, you can do it in 30 seconds, according to Bob Hallewell, an email consultant at Expert Messaging, who has advised more than 2,000 organisations on how to change their inbox culture. “Simply set up a folder called ‘Old inbox’ and move every single message across. That gives you some breathing space, and gets over the psychological block that an overfilled inbox can cause.”

Then you need to set aside some time to clear your old inbox. “The first step is to sort your messages out by sender [using the tab at the top of the messages]. You know who sends you rubbish, so you can quickly delete their messages in blocks,” Hallewell says.

Next, sort them by subject. “That breaks your emails down into conversations. With any luck, the latest email should have the full history of the whole conversation, and you can delete the previous messages,” he says. Now look for any urgent messages and tackle them immediately. “An email is rarely urgent for the person who receives it, although it is often urgent for the person who sent it.” Finally, sort them by date, and tackle the most recent messages first. Management consultants say you should never pick up the same piece of paper more than once, so you should never click on any email twice. If you’re feeling bold you could simply delete any messages more than, for example, one month old. If they were important you could take the view that the person would have resent it or tried to contact you another way. “Ask yourself how many times you have found some old email really useful? The answer is likely to be hardly ever,” Hallewell says.

 If, deep in your heart, you know you will never get round to answering some ancient email put it out of its misery and delete it. Once you have cleared the backlog of messages you have to prevent it from squirming out of control again. The best way is to stop non-urgent messages reaching your inbox in the first place, internet trainer and consultant Karen Blakeman says. “Start with a good spam filter. Then use RSS feeds to divert non-urgent email away from your inbox. I divert mine into Google Reader so I'm not clogging up my inbox. And take the time to unsubscribe to any newsletters, updates and offers you never read.”

Another option is to set up your email so that messages you know you won't be interested in are immediately forwarded to a junk mail folder. There are sites explaining how to do this in Lotus Notes and Microsoft Outlook. “If it gets clogged up with rubbish simply abandon the account,” Blakemore says. Be disciplined. As an ideal your inbox should never hold more than around 25 messages, roughly the number that fit on the typical computer screen. Achieve that and you will never again be prevented from sending out messages to clog up other people’s inboxes.