I take it you are referring to Thunderbird, the Mozilla mail client? I get such lags as well, in a number of things and sometimes, especially if I have a large (>1000) number of messages in a directory it can all but freeze up. I use it on an apple, by the way, it's not a debian issue. I imagine that there's a Firebird specific mailing list but I don't know. I've only just joined the Mozilla mailing lists. Regards, Max