I’ve written before about one of my favourite features of Apple Mail – the ability to select multiple mailboxes at once and see a merged list of messages which you can sort, search etc. If I’m looking for all my correspondence on a particular subject or with a particular person, I’ll often select all my (6) inboxes, sent mail boxes, and probably a few archives as well, and then type into the search box. I’ve never seen this merging of mailboxes work so well on another mail viewer; it’s the main thing I miss when using the otherwise excellent Thunderbird.
Once you’re working within some search query or other particular view of your mail, though, how do you get back to your normal view to make a quick check on something else without losing your current setup? It’s easy, I’ve just realised. On the File menu there’s a ‘New Viewer Window’ option. This gives you a duplicate of the main window in which you can work completely independently, so you can pop up a new window for a particular search, have separate windows for working in different email accounts etc.