diff --git a/doc/guix.texi b/doc/guix.texi
index 808fbdceb4..c159e12b1b 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -9964,8 +9964,8 @@ Defaults to @samp{""}.
 
 @deftypevr {@code{dovecot-configuration} parameter} string postmaster-address
 Address to use when sending rejection mails.
-Default is postmaster@@<your domain>.  %d expands to recipient domain.
-Defaults to @samp{""}.
+%d expands to recipient domain.
+Defaults to @samp{"postmaster@@%d"}.
 @end deftypevr
 
 @deftypevr {@code{dovecot-configuration} parameter} string hostname
diff --git a/gnu/services/mail.scm b/gnu/services/mail.scm
index d94532c353..cb0f119f43 100644
--- a/gnu/services/mail.scm
+++ b/gnu/services/mail.scm
@@ -1352,7 +1352,7 @@ regeneration entirely.")
    "SSL crypto device to use, for valid values run \"openssl engine\".")
 
   (postmaster-address
-   (string "")
+   (string "postmaster@%d")
    "Address to use when sending rejection mails.
 Default is postmaster@@<your domain>.  %d expands to recipient domain.")