Our panel of experts this month comprises Gavin Russell, technical director of consultancy Wavex, Chris Green, technical editor of Computing magazine, David Quarterman, chief executive of independent software house Corexe, Ollie Ross, researcher, Corporate IT Forum, and independent consultant Gill Hunt.

If you have a problem you would like to see answered, email it to online.feedback@theguardian.com or post it to Online, The Guardian, 119 Farringdon Road, London EC1R 3ER.

· An employee has sent an email containing a rather explicit joke intended for a colleague to the company's biggest customer. Is there anyway I can retrieve the email and stop this happening again?

GR: Outlook does support a message recall facility, which can be used to retrieve messages sent in error. This is accessed by going to the offending sent message, choosing the "Actions" menu item and then the "Recall message" option. However, one word of warning: this function relies on the addressee having an email system that understands the recall request. Therefore, if the recipient is using an incompatible system, they will not only see the message you wished to recall but also a "recall" email, which might draw extra attention to the message.

· I am a partner in a consultancy, at the heart of which are two senior PR consultants, one based in London and one in Reading. We rely ever more heavily on email contact databases and would like to synchronise them without rekeying information. We keep our costs low on behalf of clients, and as there are only two of us, networking the computers seems an expensive option.

OR: Networking doesn't need to be expensive. As long as you both live in areas with access to broadband internet, you can buy a simple hardware virtual private network (VPN) and firewall device that gives you the ability to send data to each other and synchronise databases quickly and easily, all without the need for a server.

This should solve your problem, although it will mean one of you has to keep hold of the master copy and have your computer switched on 24 hours a day. If you both meet up regularly, the other, more low-tech, option is to hold the master copy in a third location and update as and when you meet.

· I have a PocketPC with Bluetooth, which works fine except occasionally I get a "Bluetooth stack cannot be loaded" error message. It seems to work again when I reset the thing, but I am concerned about what is going wrong and what else might be happening under the bonnet. What is causing it, and how do I stop it?

GH: You don't say what make of PocketPC this is, but the message you are getting is a common problem with the iPaq series from Compaq. It means that the PocketPC hasn't got enough memory to load the Bluetooth software, probably because you are running too many other programs at the same time.

To prevent this make sure that you have closed down any games or other software before connecting via Bluetooth.

There is an updated version of the iPaq software available from www.compaq.com/support which should at least make the messages more sensible.

· I have been told I should have a firewall for my office network. There seems to be a lot of options available at a range of costs, but we don't want to pay a fortune. Can anyone recommend a cheap but effective system and explain how it will work?

DQ: If you use Microsoft-based servers (Windows NT 4 or later), you have a firewall built in, although you may not be using it. But if you don't want all your eggs in one basket, try ZoneAlarm from ZoneLabs or Wingate from Deerfield. Both are cheap and easy to install and can run on the server that you use to connect to the internet.

Both work by applying techniques that make your entry to the internet almost invisible and if you are invisible, nobody can hack you. You can test your vulnerability to attack by going to www.grc.com and running the Shields Up utility.

· We, like many companies, back up our data on a daily basis. However, when I return to the office in the morning I often discover that operation hasn't been successful. Is there a quick way to ensure the operation completes before I go home in the evening?

GR: It is not a good idea to run a back-up during office hours, because many more files are in use, which can cause problems. The usual reason for back-up failure is because the back-up software is attempting to replicate files that require backing up in a particular way or shouldn't be backed up at all.

However, one should remember that when the server registers a back-up failure, this does not mean everything has failed. An examination of the log files will highlight what data has and has not been replicated.

· I want to use broadband, but it is not available on my BT exchange. I have been told satellite broadband is an economical option now for small businesses, but I don't understand all this stuff about latency and contention. Can someone explain the issues and pitfalls?

DQ: If ADSL is not available to you, satellite technology might be an option. But, if you are a "standard" internet user, browsing websites and information surfing, the effects of latency - the time taken for your request to travel from your PC through the uplink to the satellite and back - might wipe out speed gains that you expect over a 56K modem.

If you regularly download large files, this delay might not be noticeable and you will get much better throughput.

Contention is less problematic on satellite (compared with ADSL), because sophisticated algorithms are used to prevent any one user from hogging the bandwidth.

· We have an office email system that uses a dial-up connection based on Macs, using the Eudora email program. I would like to be able to check emails remotely, using my mobile phone, but I want to be able to keep the original email on the office system so that it can be viewed by colleagues and archived. I can check emails using webmail, but this only shows unchecked emails that haven't yet been downloaded in the office. We are a small business with fewer than 10 computers. I have a Wap-enabled phone.

CG: Some webmail systems support Wap and allow you to view all the mail in your mailbox, not just the stuff that is marked unread. One such service is Mail2Web, which directly accesses and displays the contents of your mailbox, rather than just copying unread messages into a webmail account. You can access the service via Wap, which is free, at mail2web.com/wap. Remember that if you download mail to your computer, most email clients by default delete the contents of the mailbox after download, so select the "Leave mail on the server" option in your email software preferences to retain all your mail for use via webmail or Wap.