diff --git a/Dockerfile b/Dockerfile
index 9247748..4f6372e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM docker.io/alpine:3.17 as builder
+FROM docker.io/alpine:3.18 as builder
 
 RUN apk --no-cache add \
   rpcgen \
@@ -16,15 +16,15 @@ RUN apk --no-cache add \
   icu-dev \
   inotify-tools-dev
 
-ENV SHA256_SUM_DOVECOT=caa832eb968148abdf35ee9d0f534b779fa732c0ce4a913d9ab8c3469b218552
-ENV DOVECOT_FILENAME=dovecot-2.3.20.tar.gz
+ENV SHA256_SUM_DOVECOT=05b11093a71c237c2ef309ad587510721cc93bbee6828251549fc1586c36502d
+ENV DOVECOT_FILENAME=dovecot-2.3.21.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 tar xzf $DOVECOT_FILENAME -C /tmp/dovecot --strip 1
 
-ENV SHA256_SUM_PIGEONHOLE=ae32bd4870ea2c1328ae09ba206e9ec12128046d6afca52fbbc9ef7f75617c98
-ENV PIGEONHOLE_FILENAME=dovecot-2.3-pigeonhole-0.5.20.tar.gz
+ENV SHA256_SUM_PIGEONHOLE=1ca71d2659076712058a72030288f150b2b076b0306453471c5261498d3ded27
+ENV PIGEONHOLE_FILENAME=dovecot-2.3-pigeonhole-0.5.21.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
@@ -56,7 +56,7 @@ RUN cd /tmp/pigeonhole && \
   --disable-static && \
   make && make install
 
-FROM docker.io/thallian/confd-env:3.17-3.1.3.0
+FROM docker.io/thallian/confd-env:3.18-3.1.5.0
 
 COPY --from=builder /lib/dovecot/ /lib/dovecot/
 COPY --from=builder /libexec/dovecot/ /libexec/dovecot/
@@ -67,21 +67,21 @@ COPY --from=builder /sbin/dovecot /sbin/dovecot
 COPY --from=builder /bin/sieve* /bin/
 
 RUN apk --no-cache add \
-    libsodium \
-    libbz2 \
-    zlib \
-    xz-libs \
-    lz4-libs \
-    lz4 \
-    linux-pam \
-    openssl \
-    ssmtp \
-    ca-certificates \
-    lua5.1-libs \
-    lua5.1-rapidjson \
-    curl \
-    inotify-tools \
-    libssl3
+  libsodium \
+  libbz2 \
+  zlib \
+  xz-libs \
+  lz4-libs \
+  lz4 \
+  linux-pam \
+  openssl \
+  ssmtp \
+  ca-certificates \
+  lua5.1-libs \
+  lua5.1-rapidjson \
+  curl \
+  inotify-tools \
+  libssl3
 
 RUN addgroup -g 150 dovecot
 RUN adduser -u 140 -h /dev/null -H -s /sbin/nologin -D -G dovecot dovecot