diff --git a/changelog/unreleased/41617 b/changelog/unreleased/41617
new file mode 100644
index 00000000000..2cd6652482d
--- /dev/null
+++ b/changelog/unreleased/41617
@@ -0,0 +1,9 @@
+Bugfix: Add missing space to mail footer signature delimiter
+
+We've fixed the signature delimiter in the email footer templates. The delimiter
+on the first line was missing the trailing space required by the signature block
+convention (RFC 3676), so mail clients were unable to recognize and collapse the
+signature. The delimiter is now correctly written as "-- " (dash-dash-space).
+
+https://github.com/owncloud/core/issues/41364
+https://github.com/owncloud/core/pull/41617
diff --git a/core/templates/html.mail.footer.php b/core/templates/html.mail.footer.php
index a024a485753..69e41947212 100644
--- a/core/templates/html.mail.footer.php
+++ b/core/templates/html.mail.footer.php
@@ -1,4 +1,4 @@
---<br>
+-- <br>
 <?php p($theme->getName()); ?> -
 <?php p($theme->getSlogan()); ?>
 <br><a href="<?php p($theme->getBaseUrl()); ?>"><?php p($theme->getBaseUrl());?></a>
diff --git a/core/templates/plain.mail.footer.php b/core/templates/plain.mail.footer.php
index f23600d9a3f..efbe9f75ba7 100644
--- a/core/templates/plain.mail.footer.php
+++ b/core/templates/plain.mail.footer.php
@@ -1,4 +1,4 @@
---
+-- 
 <?php p($theme->getName() . ' - ' . $theme->getSlogan()); ?>
 <?php
 p("\n" . $theme->getBaseUrl());