diff --git a/mailsrv/Containerfile b/mailsrv/Containerfile
index 49ba0d1..c195f48 100644
--- a/mailsrv/Containerfile
+++ b/mailsrv/Containerfile
@@ -29,7 +29,7 @@ ARG FILESUID=5000
 ARG DEBIAN_FRONTEND=noninteractive
 
 # install packages we want
-RUN apt update -y && apt install -y rsyslog postfix dovecot-imapd dovecot-lmtpd dovecot-sieve cron
+RUN apt update -y && apt install -y rsyslog postfix dovecot-imapd dovecot-lmtpd dovecot-sieve cron opendkim
 
 # add virtual mail user
 RUN addgroup --gid ${FILESUID:?} vmail && \