Anti-virus software invades the Outlook Express program to try and intercept (incoming and, in some cases, outgoing) messages that might contain a virus. The problem with this approach is that the antivirus software can trigger the destruction of an entire message folder or the entire message store, when it attempts to remove a message containing a potential virus. Because of the fragility of the OE message store structure and its propensity for destruction, this applies to just about any anti-virus program that touches the OE message store.
Interestingly, some time ago Symantec/Norton carried on their website a message to this effect - this was later withdrawn.
Norton invented email scanning and here's what they said: "Disabling Email Scanning does not leave you unprotected against viruses that are distributed as email attachments. Norton AntiVirus Auto-Protect scans incoming files as they are saved to your hard drive, including email and email attachments. Email Scanning is just another layer on top of this.”…………
"...your computer is protected if Auto-Protect is enabled. Auto-Protect scans any incoming files, including email attachments, when the files are saved to your hard drive."
To prevent the possibility of Outlook Express destructing, turn off email scanning in your antivirus software. You will still be protected against infection. If you attempt to open a message attachment containing a potential virus, then your anti-virus software will recognize that you are attempting to infect your system, and will block you from doing so. The best practice on the user's part is to save an attachment and then scan it with the anti-virus software prior to opening it. Messages opened themselves (if you have the latest security updates from Windows Update) will not infect your system -- only attachments. You do not need additional email scanning on top of your system being continuously scanned by antivirus software, so turn off email scanning to prevent destruction of your message store.
In addition, sometimes your ISP's server may "timeout" waiting for your system to finish scanning your email before it is received or being sent out. That then can become another problem to sort out. THIS IS MY PROBLEM!