-If it is a string then that string should be an external program
-which must take a single argument (searched string) and output a
-list of completion candidates, one per line.
-
-Alternatively, it can be the symbol `internal', in which case
-internal completion is used; the variable
-`notmuch-address-internal-completion' can be used to customize
-this case.
-
-Finally, if this variable is nil then address completion is
-disabled."
+If this is a string, then that string should be an external
+program, which must take a single argument (searched string)
+and output a list of completion candidates, one per line.
+
+If this is the symbol `internal', then an implementation is used
+that relies on the \"notmuch address\" command, but does not use
+any third-party (i.e. \"external\") programs.
+
+If this is the symbol `as-is', then Notmuch does not modify the
+value of `message-completion-alist'. This option has to be set to
+this value before `notmuch' is loaded, otherwise the modification
+to `message-completion-alist' may already have taken place. This
+setting obviously does not prevent `message-completion-alist'
+from being modified at all; the user or some third-party package
+may still modify it.
+
+Finally, if this is nil, then address completion is disabled."