diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2292ac20..2d237098 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,11 +13,13 @@ All notable changes to this project will be documented in this file. The format
 
 ### Updated
 
-- **Externally installed software**
-  - bumped `jaq` from `2.1.0` to [`2.3.0`](https://github.com/01mf02/jaq/releases/tag/v2.3.0) ([#4557](https://github.com/docker-mailserver/docker-mailserver/pull/4557))
-  - bumped `step` CLI from `0.28.2` to [`0.28.7`](https://github.com/smallstep/cli/releases/tag/v0.28.7)) ([#4557](https://github.com/docker-mailserver/docker-mailserver/pull/4557))
+- **Internal:**
+  - Aligning with the change in upstream Debian, APT package repositories added by DMS have migrated the format from `.list` to `.sources` ([DEB822](https://repolib.readthedocs.io/en/latest/deb822-format.html)) ([#4556](https://github.com/docker-mailserver/docker-mailserver/pull/4556))
+  - Third-party sourced CLI tools updated ([#4557](https://github.com/docker-mailserver/docker-mailserver/pull/4557)):
+    - `jaq` from `2.1.0` to [`2.3.0`](https://github.com/01mf02/jaq/releases/tag/v2.3.0)
+    - `step` CLI from `0.28.2` to [`0.28.7`](https://github.com/smallstep/cli/releases/tag/v0.28.7))
 - **Dovecot**
-  - Bumped Xapian version from `1.9` to [`1.9.1`](https://github.com/grosjo/fts-xapian/releases/tag/1.9.1) ([#4557](https://github.com/docker-mailserver/docker-mailserver/pull/4557)), which includes Dovecot 2.4 compatibility
+  - Updated the FTS plugin Xapian from `1.9` to [`1.9.1`](https://github.com/grosjo/fts-xapian/releases/tag/1.9.1) which adds Dovecot 2.4 compatibility ([#4557](https://github.com/docker-mailserver/docker-mailserver/pull/4557))
 
 ## [v15.1.0](https://github.com/docker-mailserver/docker-mailserver/compare/v15.1.0...HEAD)
 
diff --git a/target/scripts/build/packages.sh b/target/scripts/build/packages.sh
index b846a3cb..48229f9b 100644
--- a/target/scripts/build/packages.sh
+++ b/target/scripts/build/packages.sh
@@ -161,10 +161,15 @@ function _install_dovecot() {
     # - 2.3.21: https://salsa.debian.org/debian/dovecot/-/tree/stable/bookworm-backports
 
     _log 'trace' 'Adding third-party package repository (Dovecot)'
-    curl -fsSL https://repo.dovecot.org/DOVECOT-REPO-GPG-2.4 | gpg --dearmor > /usr/share/keyrings/upstream-dovecot.gpg
-    echo \
-      "deb [signed-by=/usr/share/keyrings/upstream-dovecot.gpg] https://repo.dovecot.org/ce-2.4-latest/debian/${VERSION_CODENAME} ${VERSION_CODENAME} main" \
-      > /etc/apt/sources.list.d/upstream-dovecot.list
+    curl -fsSL https://repo.dovecot.org/DOVECOT-REPO-GPG-2.4 \
+      | gpg --dearmor >/usr/share/keyrings/upstream-dovecot.gpg
+    cat >/etc/apt/sources.list.d/upstream-dovecot.sources <<EOF
+Types: deb
+URIs: https://repo.dovecot.org/ce-2.4-latest/debian/${VERSION_CODENAME}
+Suites: ${VERSION_CODENAME}
+Components: main
+Signed-By: /usr/share/keyrings/upstream-dovecot.gpg
+EOF
 
     # Refresh package index:
     apt-get "${QUIET}" update
@@ -188,10 +193,15 @@ function _install_rspamd() {
   # NOTE: Debian 12 provides Rspamd 3.4 (too old) and Rspamd discourages it's use
 
   _log 'trace' 'Adding third-party package repository (Rspamd)'
-  curl -fsSL https://rspamd.com/apt-stable/gpg.key | gpg --dearmor > /usr/share/keyrings/upstream-rspamd.gpg
-  echo \
-    "deb [signed-by=/usr/share/keyrings/upstream-rspamd.gpg] https://rspamd.com/apt-stable/ ${VERSION_CODENAME} main" \
-    > /etc/apt/sources.list.d/upstream-rspamd.list
+  curl -fsSL https://rspamd.com/apt-stable/gpg.key \
+    | gpg --dearmor >/usr/share/keyrings/upstream-rspamd.gpg
+  cat >/etc/apt/sources.list.d/upstream-rspamd.sources <<EOF
+Types: deb
+URIs: https://rspamd.com/apt-stable/
+Suites: ${VERSION_CODENAME}
+Components: main
+Signed-By: /usr/share/keyrings/upstream-rspamd.gpg
+EOF
 
   # Refresh package index:
   apt-get "${QUIET}" update