diff --git a/docker/postfix/Dockerfile b/docker/postfix/Dockerfile
index c5831bfdb0979585158bafc8c3e463b85f443c3f..d6ee7267fa7baff129e25f80e9917190c4742d1d 100644
--- a/docker/postfix/Dockerfile
+++ b/docker/postfix/Dockerfile
@@ -4,7 +4,7 @@ FROM tozd/postfix:ubuntu-focal
 VOLUME /etc/sympa/shared
 
 RUN apt-get update -q -q && \
- apt-get install adduser curl dnsutils openssh-client opendkim opendkim-tools --yes --force-yes && \
+ apt-get install adduser curl dnsutils openssh-client opendkim opendkim-tools spamassassin --yes --force-yes && \
  adduser --system --group mailpipe --no-create-home --home /nonexistent && \
  cp /etc/postfix/main.cf /etc/postfix/main.cf.orig && \
  cp /etc/postfix/master.cf /etc/postfix/master.cf.orig
@@ -15,4 +15,8 @@ RUN curl https://okean.com/sinokoreacidr.txt \
 	| sed -e 's/\(China\|Korea\)/REJECT Source IP blocked \1/g' \
 	> /etc/postfix/sinokorea.cidr
 
+RUN sed -i -e 's/^\(smtp.*smtpd\)$/\1 -o content_filter=spamassassin/' /etc/postfix/master.cf
+
+RUN echo 'rewrite_header Subject *****SPAM*****' >> /etc/spamassassin/local.cf
+
 COPY ./etc /etc
diff --git a/docker/postfix/etc/postfix/master.cf.append b/docker/postfix/etc/postfix/master.cf.append
index b5b84b6b4ec9e5e011c72d08599e49f3998e6f64..83a9724b6629c6273c830831ac51ea3fae4719c1 100644
--- a/docker/postfix/etc/postfix/master.cf.append
+++ b/docker/postfix/etc/postfix/master.cf.append
@@ -14,3 +14,4 @@ sympabounce	unix	-	n	n	-	-	pipe
 sympabouncedomain	unix	-	n	n	-	-	pipe
   -o soft_bounce=yes
   flags=RF user=mailpipe:mailpipe argv=/usr/bin/ssh -i /etc/sympa/shared/id_rsa -o UserKnownHostsFile=/etc/sympa/shared/known_hosts -T sympa@sympa bouncequeue sympa@${domain}
+spamassassin unix -     n       n       -       -       pipe user=spamassassin argv=/usr/bin/spamc -f -e /usr/sbin/sendmail -oi -f ${sender} ${recipient}