diff --git a/README.rst b/README.rst
index 71cd68b..61ce1c0 100644
--- a/README.rst
+++ b/README.rst
@@ -23,3 +23,10 @@ By default, the following components are installed:
 * Postfix
 * Dovecot
 * Amavis (with SpamAssassin and ClamAV)  
+
+If you want to follow details of installation process, use --debug
+
+At the end of the process, you should consider updating virus database with this command:: 
+
+  freshclam
+  /etc/init.d/clamav-daemon restart
diff --git a/modoboa_installer/scripts/dovecot.py b/modoboa_installer/scripts/dovecot.py
index 36dc586..9bbf8b9 100644
--- a/modoboa_installer/scripts/dovecot.py
+++ b/modoboa_installer/scripts/dovecot.py
@@ -50,20 +50,19 @@ class Dovecot(base.Installer):
 
     def post_run(self):
         """Additional tasks."""
-        if self.dbengine != "postgres":
-            return
-        dbname = self.config.get("modoboa", "dbname")
-        dbuser = self.config.get("modoboa", "dbuser")
-        dbpassword = self.config.get("modoboa", "dbpassword")
-        backend = database.get_backend(self.config)
-        backend.load_sql_file(
-            dbname, dbuser, dbpassword,
-            self.get_file_path("install_modoboa_postgres_trigger.sql")
-        )
-        backend.load_sql_file(
-            dbname, dbuser, dbpassword,
-            self.get_file_path("fix_modoboa_postgres_schema.sql")
-        )
+        if self.dbengine == "postgres":
+            dbname = self.config.get("modoboa", "dbname")
+            dbuser = self.config.get("modoboa", "dbuser")
+            dbpassword = self.config.get("modoboa", "dbpassword")
+            backend = database.get_backend(self.config)
+            backend.load_sql_file(
+                dbname, dbuser, dbpassword,
+                self.get_file_path("install_modoboa_postgres_trigger.sql")
+            )
+            backend.load_sql_file(
+                dbname, dbuser, dbpassword,
+                self.get_file_path("fix_modoboa_postgres_schema.sql")
+            )
         for f in glob.glob("{}/*".format(self.get_file_path("conf.d"))):
             shutil.copy(f, "{}/conf.d".format(self.config_dir))
 
diff --git a/modoboa_installer/scripts/files/amavis/amavis_mysql_2.10.1.sql b/modoboa_installer/scripts/files/amavis/amavis_mysql_2.10.1.sql
index 0cb3d82..a7f2d3c 100644
--- a/modoboa_installer/scripts/files/amavis/amavis_mysql_2.10.1.sql
+++ b/modoboa_installer/scripts/files/amavis/amavis_mysql_2.10.1.sql
@@ -162,7 +162,8 @@ CREATE TABLE msgs (
   subject    varchar(255)  CHARACTER SET utf8 COLLATE utf8_bin  DEFAULT '',
                                         -- mail Subject header field, UTF8
   host       varchar(255)  NOT NULL,    -- hostname where amavisd is running
-  PRIMARY KEY (partition_tag,mail_id)
+  PRIMARY KEY (partition_tag,mail_id),
+  INDEX (mail_id),
   FOREIGN KEY (sid) REFERENCES maddr(id) ON DELETE RESTRICT
 ) ENGINE=InnoDB;
 CREATE INDEX msgs_idx_sid      ON msgs (sid);
@@ -191,7 +192,7 @@ CREATE TABLE msgrcpt (
   wl         char(1)  DEFAULT ' ',       -- sender whitelisted by this recip
   bspam_level float,                     -- per-recipient (total) spam level
   smtp_resp  varchar(255)  DEFAULT '',   -- SMTP response given to MTA
-  PRIMARY KEY (partition_tag,mail_id,rseqnum)
+  PRIMARY KEY (partition_tag,mail_id,rseqnum),
   FOREIGN KEY (rid)     REFERENCES maddr(id)     ON DELETE RESTRICT,
   FOREIGN KEY (mail_id) REFERENCES msgs(mail_id) ON DELETE CASCADE
 ) ENGINE=InnoDB;
@@ -208,7 +209,7 @@ CREATE TABLE quarantine (
   mail_id    varbinary(16) NOT NULL,     -- long-term unique mail id
   chunk_ind  integer unsigned NOT NULL,  -- chunk number, starting with 1
   mail_text  blob          NOT NULL,     -- store mail as chunks of octets
-  PRIMARY KEY (partition_tag,mail_id,chunk_ind)
+  PRIMARY KEY (partition_tag,mail_id,chunk_ind),
   FOREIGN KEY (mail_id) REFERENCES msgs(mail_id) ON DELETE CASCADE
 ) ENGINE=InnoDB;
 
diff --git a/modoboa_installer/scripts/files/amavis/amavis_mysql_2.7.1.sql b/modoboa_installer/scripts/files/amavis/amavis_mysql_2.7.1.sql
index 710d290..4b6bc23 100644
--- a/modoboa_installer/scripts/files/amavis/amavis_mysql_2.7.1.sql
+++ b/modoboa_installer/scripts/files/amavis/amavis_mysql_2.7.1.sql
@@ -165,6 +165,7 @@ CREATE TABLE msgs (
                                         -- mail Subject header field, UTF8
   host       varchar(255)  NOT NULL,    -- hostname where amavisd is running
   PRIMARY KEY (partition_tag,mail_id),
+  INDEX (mail_id),
   FOREIGN KEY (sid) REFERENCES maddr(id) ON DELETE RESTRICT
 ) ENGINE=InnoDB;
 CREATE INDEX msgs_idx_sid      ON msgs (sid);