Update mail package set.

pkgsets/mail_utils.nix

@@ -1,14 +1,15 @@
 {
-  config,
   pkgs,
   ...
 }: {
   config.machine.pkgsets.mail_utils.pkgs = with pkgs; [
-    fetchmail
-    isync
+    aerc
+    abook
+    pizauth
+    libsecret # to request passwords from keyring
+    notmuch
+    (isync.override { withCyrusSaslXoauth2 = true; })
     mailutils
-    gitpkgs.mu
-    pandoc
-    postfix
+    pandoc # to convert messages
   ];
 }