diff --git a/puppet/zulip/files/postfix/access b/puppet/zulip/files/postfix/access
index 265bcf70ce..0f4450aea2 100644
--- a/puppet/zulip/files/postfix/access
+++ b/puppet/zulip/files/postfix/access
@@ -4,6 +4,6 @@
 
 /\+.*@/         OK
 /\..*@/         OK
-/^mm/           OK
+/^mm.{32}@/     OK
 
 /^postmaster@/  OK
diff --git a/puppet/zulip/templates/postfix/virtual.erb b/puppet/zulip/templates/postfix/virtual.erb
index 09c8db7d93..d258547632 100644
--- a/puppet/zulip/templates/postfix/virtual.erb
+++ b/puppet/zulip/templates/postfix/virtual.erb
@@ -1,7 +1,7 @@
 if /@<%= Regexp.escape(@postfix_mailname) %>\.?$/
 # Changes to this list require a corresponding change to `access` as
 # well.
-/\+.*@/  zulip@localhost
-/\..*@/  zulip@localhost
-/^mm/    zulip@localhost
+/\+.*@/     zulip@localhost
+/\..*@/     zulip@localhost
+/^mm.{32}@/ zulip@localhost
 endif