Had a situation where Outlook Express users (Japanese version) in our Japan office were not able to retrieve any POP3 emails. Our HTML-based newsletter, BBDO AsiaNews, triggered the problem. If the newsletter was deleted from the server (using Webmail or by manually telnetting to port 110) messages were immediately retrieved, as usual. In Outlook Express, the retrieval of messages would simply get "stuck". Error on the server was "Connection timed out". The server and the clients were on the same LAN. Troubleshooting was difficult not only because I was in Hong Kong and the users were in Japan, but also because both the Windows system and the Outlook Express program were entirely in Japanese! I ruled out the newsletter as being the problem because none of the 800 or so other recipients had any problem. I also doubted that Outlook Express was the problem because users of Outlook Express in our Korea and Taiwan offices who were also using localized versions didn't have the problem either. I recalled that many antivirus packages intercept data between mail servers and clients so that viruses can be caught before actually hitting the clients' Inboxes. With the help of "Junko" in our Japan office helping to change settings and do tests, we determined that the "Mail Search" (or "POP Trap") component of Trend Micro's "PC-Cillin" (and "Virus Buster" on some of their PCs) antivirus software was causing the problem.