Hi! I'm using this configuration: Windows Vista Business Dutch SP1. Mozilla Thunderbird Add-ins: Dictionary Dutch, English, German, French Display Quota Lightning Message Filter Import/Export Custom settings: mail.check_all_imap_folders_for_new mail.imap.use_status_for_biff IMAP with XS4ALL ESS4 Dutch When I enable the ESS E-mail scanner all my e-mails are being received tripple, and also being put in tipple in the IMAP mailbox. This doesn't only causes a problem on the PC where I got ESS installed (laptop), but also at other PC's (desktop, webmail) because there are physically 3 e-mails. I haven't done any advanced troubleshooting yet but it's ESS that's causing it. With ESS disabled: problem gone. With ESS enabled and changing all possible TB settings: problem there. At other PC (Vis Biss, TB, same settings and plug-ins) with KAV 7: no problem.