diff --git a/Dockerfile b/Dockerfile
index 9f6a4701..ee879a50 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -24,6 +24,7 @@ RUN echo "deb http://ftp.debian.org/debian stretch-backports main" | tee -a /etc
   # TODO installing postfix with --no-install-recommends makes "checking ssl: generated default cert works correctly" fail
   apt-get -y install --no-install-recommends \
     amavisd-new \
+    apt-transport-https \
     arj \
     binutils \
     bzip2 \
@@ -76,7 +77,11 @@ RUN echo "deb http://ftp.debian.org/debian stretch-backports main" | tee -a /etc
     xz-utils \
     zoo \
     && \
-  apt-get -t stretch-backports -y install --no-install-recommends \
+  curl https://repo.dovecot.org/DOVECOT-REPO-GPG | gpg --import && \
+  gpg --export ED409DA1 > /etc/apt/trusted.gpg.d/dovecot.gpg && \
+  echo "deb https://repo.dovecot.org/ce-2.3-latest/debian/stretch stretch main" > /etc/apt/sources.list.d/dovecot.list && \
+  apt-get update -q --fix-missing && \
+  apt-get -y install --no-install-recommends \
     dovecot-core \
     dovecot-imapd \
     dovecot-ldap \
@@ -85,6 +90,9 @@ RUN echo "deb http://ftp.debian.org/debian stretch-backports main" | tee -a /etc
     dovecot-pop3d \
     dovecot-sieve \
     && \
+  sed -i 's/CERTDIR=.*/CERTDIR=\/etc\/dovecot\/ssl/g' /usr/share/dovecot/mkcert.sh && \
+  sed -i 's/KEYDIR=.*/KEYDIR=\/etc\/dovecot\/ssl/g' /usr/share/dovecot/mkcert.sh && \
+  sed -i 's/KEYFILE=.*/KEYFILE=\$KEYDIR\/dovecot.key/g' /usr/share/dovecot/mkcert.sh && \
   apt-get autoclean && \
   rm -rf /var/lib/apt/lists/* && \
   rm -rf /usr/share/locale/* && \