The Debian packaging of mairix is maintained in git, using the merging
workflow described in dgit-maint-merge(7).  There isn't a patch queue
that can be represented as a quilt series.

A detailed breakdown of the changes is available from their canonical
representation - git commits in the packaging repository.  For
example, to see the changes made by the Debian maintainer in the first
upload of upstream version 1.2.3, you could use:

    % git clone https://git.dgit.debian.org/mairix
    % cd mairix
    % git log --oneline 1.2.3..debian/1.2.3-1 -- . ':!debian'

(If you have dgit, use `dgit clone mairix`, rather than plain `git
clone`.)

A single combined diff, containing all the changes, follows.
--- mairix-0.24.orig/mairixrc.5
+++ mairix-0.24/mairixrc.5
@@ -61,8 +61,8 @@ maildir folders.
 .br
 If any IMAP source folders are specified or the results folder is an IMAP
 folder, this defines the host name of the IMAP server. The port is
-currently always 143. This option is mutually exclusive with the
-'imap_pipe' option.
+currently always 143. This option is mutually exclusive with the 'imap_pipe'
+option.
 
 .TP
 .BI imap_pipe= shell-command
