Struct IndexFields 

pub struct IndexFields<'a> {
    pub number: usize,
    pub status: char,
    pub flag: char,
    pub mark: char,
    pub date: &'a str,
    pub from: &'a str,
    pub size: &'a str,
    pub lines: Option<usize>,
    pub list: Option<&'a str>,
    pub hidden: Option<usize>,
    pub label: Option<&'a str>,
    pub subject: &'a str,
}

Fields

number: usize

status: char

flag: char

mark: char

Third %Z slot: ‘*’ tagged, or how the mail addresses me (‘+’ only me in To, ‘T’ me among others, ‘C’ me in Cc).

date: &'a str

from: &'a str

size: &'a str

lines: Option<usize>

Body line count; None (header-only cache file) makes %l empty, so %?l?…&…? shows its else branch.

list: Option<&'a str>

Mailing-list name (List-Id); %L shows “To ” instead of the author when set.

hidden: Option<usize>

Messages hidden under this collapsed thread root (%M).

label: Option<&'a str>

mutt’s X-Label, for %y.

subject: &'a str