In the message list you can't select multiple discontiguos messages with control and space. If you press control you can move the focus without losing the selection, but the space bar doesn't toggle the selection of the focused message. Tested on build 20030218 (and on 1.3a and 1.3b). It used to work in 1.0. I thought this would have been reported before but I couldn't find anything on bugzilla after quite a long search.

*** This bug has been marked as a duplicate of 97434 ***

The space bar scrolls the message pane; try using Ctrl+Space.

Yes, sure, I forgot to mention that control should be kept pressed while selecting. So its press control, move with up and down, and select with space (always keeping control pressed). BTW, i think this bug is not a dupe of bug 97434, it is a dupe of bug 121049. But it doesn't matter anyway. The only detail is that bug 121049 is filed as an enhacement and I think that it should be marked as major (or at least normal), because this used to work before (in moz 1.0, for example) and the same thing works everywhere else (in outlook, in eudora, in <select multiple> tags inside mozilla). Because of this, selecting multiple discontiguous messages in mail for deleting or moving with the keyboard is much more work than before (actually it's impossible, you have to either use the mouse, or do them one at a time).