diff --git a/Dockerfile b/Dockerfile
index da9320f..3dc899a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:3.9 as builder
+FROM alpine:3.10 as builder
 
 RUN apk --no-cache add \
     rpcgen \
@@ -17,11 +17,19 @@ RUN apk --no-cache add \
     icu-dev \
     inotify-tools-dev
 
+ENV SHA256_SUM_DOVECOT=11e156ae8539e42892809cc2412c3f1a294188806969f5547191a43abd4083aa
+ENV DOVECOT_FILENAME=dovecot-2.3.7.tar.gz
+RUN wget https://www.dovecot.org/releases/2.3/$DOVECOT_FILENAME
+RUN echo "$SHA256_SUM_DOVECOT  $DOVECOT_FILENAME" | sha256sum -c - || exit 1
 RUN mkdir /tmp/dovecot
-RUN wget -qO- https://www.dovecot.org/releases/2.3/dovecot-2.3.4.tar.gz | tar -xz -C /tmp/dovecot --strip 1
+RUN tar xzf $DOVECOT_FILENAME -C /tmp/dovecot --strip 1
 
+ENV SHA256_SUM_PIGEONHOLE=783849542c272331f60e7c4d371b303f7f2b1d69828bced3094a898876ecdb63
+ENV PIGEONHOLE_FILENAME=dovecot-2.3-pigeonhole-0.5.7.tar.gz
+RUN wget https://pigeonhole.dovecot.org/releases/2.3/$PIGEONHOLE_FILENAME
+RUN echo "$SHA256_SUM_PIGEONHOLE  $PIGEONHOLE_FILENAME" | sha256sum -c - || exit 1
 RUN mkdir /tmp/pigeonhole
-RUN wget -qO- https://pigeonhole.dovecot.org/releases/2.3/dovecot-2.3-pigeonhole-0.5.4.tar.gz | tar -xz -C /tmp/pigeonhole --strip 1
+RUN tar xzf $PIGEONHOLE_FILENAME -C /tmp/pigeonhole --strip 1
 
 RUN cd /tmp/dovecot && \
     ./configure --prefix '' \