1 Mutt is, by far, my favourite mail client. It's small, configurable,
2 fast and it does not get in your way. It's a great tool.
3 
4 My setup involves various maildir: I have a decent amount of filters
5 that I use to order the mail in different directories.
6 
7 One thing that I've found annoying is switching maildir: opening ones
8 with ~3k mail takes too much time, at least on my machine. Now I think
9 that using the `threads` sorting was the culprit, but it's only a
10 guess.
11 
12 Anyway, while I was searching the manpage for a totally different
13 issue, I've found the `header_cache` settings. Quoting the manpage:
14 
15 > This variable points to the header cache database. [...] By default
16 > it is *unset* so no header caching will be used.
17 >
18 > Header caching can greatly improves speed when opening POP, IMAP HM
19 > or Maildir folders, see "caching" for details.
20 
21 There are also other relating settings, like `header_cache_compress`
22 that may be interestig.