Sorting Messages
A thread is a group of messages that are either related by subject or that have a common ancestor. Threading is the process of determining the relationship between such messages and displaying them so that those relationship are evident.
To enable and disable threading, type C-t
(vm-toggle-threads-display. In the summary buffer related
messages are grouped together and the subject part of the summary
listings of messages are indented to show hierarchical relationships.
Parent messages are displayed before their children and children are
indented a default two spaces to the right for each level of descendence
from their ancestors. The amount of indentation per level is controlled by the
variable vm-summary-thread-indent-level.
Message relationships are discovered by examining References,
In-Reply-To, and Subject headers. The first two headers are more
reliable sources of information but not all mailers provide them.
If you don't want VM to use Subject headers, set the variable
vm-thread-using-subject to nil.
If you want VM to always display messages using threads, you should set
the default value of the variable vm-summary-show-threads
non-nil in your VM init file. Exmaple:
(setq-default vm-summary-show-threads t)
Do not use setq, as this will only set the value of the variable in
a single buffer. Once you've started VM you should not change the value
of this variable. Rather you should use C-t to control the thread
display.
Note that threading is really a specialized form of sorting, and so the
value of the variable vm-move-messages-physically applies.
Sorting Messages