diff --git a/Dockerfile b/Dockerfile
index 38f65fc..7abf78e 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,7 +5,7 @@ RUN export DEBIAN_FRONTEND=noninteractive \
  && apt-get install -y --no-install-recommends \
       postfix dovecot-imapd dovecot-sqlite dovecot-lmtpd \
       dovecot-sieve dovecot-managesieved \
-      dovecot-antispam spamassassin clamav \
+      dovecot-antispam spamassassin spamc clamav \
       supervisor rsyslog \
  && apt-get clean
 
diff --git a/README.md b/README.md
index eeab223..75ddd8b 100644
--- a/README.md
+++ b/README.md
@@ -16,8 +16,8 @@ same level of functionality and still be able to host a complete mail server
 at little cost while running only FOSS, applying the KISS principle and being
 able to fine-tune some details if needed.
 
-Architecture
-============
+General architecture
+====================
 
 The mail infrastructure is based on a standard MTA-LDA :
 
@@ -33,6 +33,21 @@ Additional Web UI :
 
 All components are monitored by supervisord.
 
+Incoming e-mail
+===============
+
+Incoming e-mail is received by postfix, according to the workflow:
+- ``smtpd`` receives the message;
+- the domain is checked against the ``domains`` table;
+- if the domain matches an active domain or the source address is allowed relay, continue;
+- the mail is forwarded to Spamassassin, which appends some headers;
+- the mail is fowarded to Dovecot using ``lmtp``;
+- the local part and domain are checked against the ``users`` table;
+- the user quota is checked;
+- the mail is delivered to the local maildir.
+
+
+
 TODO
 ====
 
@@ -41,8 +56,9 @@ This is more of a roadmap than a proper TODO list. Please poke me or pull
 request if you would like to join the effort.
 
  - [x] Import vmm configuration files and get a simple postfix/dovecot running with SQLite.
- - [ ] Add support for spamassassin.
+ - [x] Add support for spamassassin.
  - [ ] Add support for clamav.
+ - [ ] Learn from user-defined spam or ham.
  - [ ] Draft a Web administration UI.
  - [ ] Implement basic features from the free (as in beer) poste.io.
  - [ ] Start using on a couple production mail servers.
diff --git a/config/postfix/master.cf b/config/postfix/master.cf
index 8f90691..7064655 100644
--- a/config/postfix/master.cf
+++ b/config/postfix/master.cf
@@ -3,6 +3,7 @@
 
 # Exposed SMTP services
 smtp      inet  n       -       -       -       -       smtpd
+  -o content_filter=spamassassin
 submission inet n       -       -       -       -       smtpd
   -o smtpd_enforce_tls=yes
   -o smtpd_sasl_auth_enable=yes
@@ -13,6 +14,7 @@ smtps     inet  n       -       -       -       -       smtpd
   -o smtpd_client_restrictions=permit_sasl_authenticated,reject
 
 # Internal postfix services
+pickup    fifo  n       -       n       60      1       pickup
 cleanup   unix  n       -       -       -       0       cleanup
 qmgr      unix  n       -       n       300     1       qmgr
 tlsmgr    unix  -       -       -       1000?   1       tlsmgr
@@ -31,3 +33,7 @@ discard   unix  -       -       -       -       -       discard
 lmtp      unix  -       -       -       -       -       lmtp
 anvil     unix  -       -       -       -       1       anvil
 scache    unix  -       -       -       -       1       scache
+
+# Utility services
+spamassassin unix -     n       n       -       -       pipe
+  user=nobody argv=/usr/bin/spamc -f -e /usr/sbin/sendmail -oi -f ${sender} ${recipient}
diff --git a/config/supervisor/supervisord.conf b/config/supervisor/supervisord.conf
index 7dc5f1f..f3cf3e3 100644
--- a/config/supervisor/supervisord.conf
+++ b/config/supervisor/supervisord.conf
@@ -1,6 +1,5 @@
 [supervisord]
 nodaemon = true
-loglevel=debug
 
 [program:postfix]
 command = /usr/lib/postfix/master -d
@@ -8,5 +7,8 @@ command = /usr/lib/postfix/master -d
 [program:dovecot]
 command = /usr/sbin/dovecot -c /etc/dovecot/dovecot.conf -F
 
+[program:spamassassin]
+command = /usr/sbin/spamd
+
 [program:rsyslog]
 command = rsyslogd -n