For testing until production stability proven.

 Get Amavis Qmail queue
# grep "release 7" /etc/centos-release
# [ "$?" = "0" ] && cos=7 || cos=8
# echo $cos
# wget -O /var/qmail/bin/qmail-queue.smtp https://github.com/qmtoaster/amavis/blob/main/qmail-queue.smtp.cos${cos}?raw=true
# chown qmailq:qmail /var/qmail/bin/qmail-queue.smtp
# chmod 4711 /var/qmail/bin/qmail-queue.smtp

 Build Your Own qmail-queue.smtp

 Install Amavis & edit config, run clamd under Amavis, start both services
# yum --enablerepo=epel,PowerTools -y install amavisd-new lz4 perl-Digest-SHA1 perl-IO-stringy
# yum --enablerepo=fedora cabextract
# wget https://www.rarlab.com/rar/rarlinux-x64-6.0.b1.tar.gz
# tar zxvf rarlinux-x64-6.0.b1.tar.gz
# cd rar
# cp rar unrar /usr/local/bin
# sed -i 's/%i.conf/amavisd.conf/' /usr/lib/systemd/system/clamd@.service
# systemctl daemon-reload
# systemctl restart clamd@scan
# vi /etc/amavisd/amavisd.conf
  $mydomain = 'domain.tld';
  $myhostname = 'mx.domain.tld';
  $notify_method = 'smtp:[127.0.0.1]:10025';
  $forward_method = 'smtp:[127.0.0.1]:10025';
# systemctl enable --now amavisd

 Create tcp rules for qmail smtp & qmail amavis
# mv /etc/tcprules.d/tcp.smtp /etc/tcprules.d/tcp.smtp.bak

tee /etc/tcprules.d/tcp.amavis.smtp  > /dev/null <<EOT
127.:allow,RELAYCLIENT="",RBLSMTPD="",NOP0FCHECK="1"
:allow,CHKUSER_RCPTLIMIT="50",CHKUSER_WRONGRCPTLIMIT="10",QMAILQUEUE="/var/qmail/bin/qmail-queue.smtp",NOP0FCHECK="1"
EOT

tee /etc/tcprules.d/tcp.smtp  > /dev/null <<EOT
127.:allow,RELAYCLIENT="",RBLSMTPD="",NOP0FCHECK="1"
:allow,CHKUSER_RCPTLIMIT="50",CHKUSER_WRONGRCPTLIMIT="10",QMAILQUEUE="/var/qmail/bin/qmail-queue",NOP0FCHECK="1"
EOT

 Edit/Create run files for qmail smtp & qmail amavis
# cp -Rp /var/qmail/supervise/smtp /var/qmail/supervise/smtp2

tee /var/qmail/supervise/smtp/run > /dev/null <<EOT
#!/bin/sh
QMAILDUID=`id -u vpopmail`
NOFILESGID=`id -g vpopmail`
MAXSMTPD=`cat /var/qmail/control/concurrencyincoming`
SMTPD="/var/qmail/bin/qmail-smtpd"
TCP_CDB="/etc/tcprules.d/tcp.amavis.smtp.cdb"
HOSTNAME=`hostname`
VCHKPW="/home/vpopmail/bin/vchkpw"
export SMTPAUTH="-"

exec /usr/bin/softlimit -m 64000000 \
     /usr/bin/tcpserver -v -R -H -l $HOSTNAME -x $TCP_CDB -c "$MAXSMTPD" \
     -u "$QMAILDUID" -g "$NOFILESGID" 0 smtp \
     $SMTPD $VCHKPW /bin/true 2>&1

EOT

tee /var/qmail/supervise/smtp2/run > /dev/null <<EOT
#!/bin/sh
QMAILDUID=`id -u vpopmail`
NOFILESGID=`id -g vpopmail`
MAXSMTPD=`cat /var/qmail/control/concurrencyincoming`
SMTPD="/var/qmail/bin/qmail-smtpd"
TCP_CDB="/etc/tcprules.d/tcp.smtp.cdb"
HOSTNAME=`hostname`
VCHKPW="/home/vpopmail/bin/vchkpw"
export SMTPAUTH="-"
export FORCETLS=0

exec /usr/bin/softlimit -m 64000000 \
     /usr/bin/tcpserver -v -R -H -l $HOSTNAME -x $TCP_CDB -c "$MAXSMTPD" \
     -u "$QMAILDUID" -g "$NOFILESGID" 0 10025 \
     $SMTPD $VCHKPW /bin/true 2>&1

EOT

tee /var/qmail/supervise/smtp2/log/run > /dev/null <<EOT
#!/bin/sh
LOGSIZE=`cat /var/qmail/control/logsize`
LOGCOUNT=`cat /var/qmail/control/logcount`
exec /usr/bin/setuidgid qmaill \
     /usr/bin/multilog t s$LOGSIZE n$LOGCOUNT \
     /var/log/qmail/smtp2 2>&1

EOT

 Add Amavis Dspam support

 Install Dspam (skip 'install per domain')
# wget https://raw.githubusercontent.com/qmtoaster/dspam/master/dspamdb.sh
# chmod 755 dspamdb.sh
# ./dpsamdb.sh

 Add Under $dspam = 'dspam'
# vi /etc/amavisd/amavisd.conf

@spam_scanners = (
   ['DSPAM', 'Amavis::SpamControl::ExtProg', 'dspam',
      [ qw(--user amavis --deliver=stdout) ],
   ],
);

 Add under 'Trust vpopmail'
# vi /etc/dspam.conf
Trust amavis

 Start & stat qmail
# qmailctl start
# qmailctl stat

send: up (pid 253068) 97100 seconds
smtp: up (pid 253065) 97100 seconds
smtp2: up (pid 253071) 97100 seconds
smtps: up (pid 253067) 97100 seconds
submission: up (pid 253073) 97100 seconds
send/log: up (pid 253064) 97100 seconds
smtp2/log: up (pid 253070) 97100 seconds
smtp/log: up (pid 253066) 97100 seconds
smtps/log: up (pid 253072) 97100 seconds
submission/log: up (pid 253069) 97100 seconds

 Test with Swaks
# swaks --to myuser@domain.tld,myuser2@domain.tld --from myuser@remotedomain.tld --server mx.domain.tld -tls
=== Trying 192.168.16.75:25...
=== Connected to 192.168.16.75.
<-  220 localhost - Welcome to Qmail Toaster Ver. 1.03-3.3.1.qt.md.el8 SMTP Server ESMTP
 -> EHLO mx.domain.tld
<-  250-localhost - Welcome to Qmail Toaster Ver. 1.03-3.3.1.qt.md.el8 SMTP Server
<-  250-STARTTLS
<-  250-PIPELINING
<-  250-8BITMIME
<-  250 SIZE 20971520
 -> STARTTLS
<-  220 ready for tls
=== TLS started with cipher TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256
=== TLS no local certificate set
=== TLS peer DN="/O=Qmail Toaster Server/OU=Test Certificate/CN=localhost"
 ~> EHLO mx.domain.tld
<~  250-localhost - Welcome to Qmail Toaster Ver. 1.03-3.3.1.qt.md.el8 SMTP Server
<~  250-PIPELINING
<~  250-8BITMIME
<~  250 SIZE 20971520
 ~> MAIL FROM:<myuser@remotedomain.tld>
<~  250 ok
 ~> RCPT TO:<myuser@domain.tld>
<~  250 ok
 ~> RCPT TO:<myuser2@domain.tld>
<~  250 ok
 ~> DATA
<~  354 go ahead
 ~> Date: Sun, 29 Nov 2020 14:58:40 -0700
 ~> To: myuser@domain.tld,myuser2@domain.tld
 ~> From: myuser@remotedomain.tld
 ~> Subject: test Sun, 29 Nov 2020 14:58:40 -0700
 ~> Message-Id: <20201129145840.009255@mx.domain.tld>
 ~> X-Mailer: swaks v20170101.0 jetmore.org/john/code/swaks/
 ~>
 ~> This is a test mailing
 ~>
 ~> .
<~  250 ok 1606687121 qp 308705
 ~> QUIT
<~  221 localhost - Welcome to Qmail Toaster Ver. 1.03-3.3.1.qt.md.el8 SMTP Server
=== Connection closed with remote host.

 All Amavis output is in the maillog (/var/log/maillog).

 Email headers will contain
X-Virus-Scanned: amavisd-new at domain.tld

 Email headers will show Amavis routing
Return-Path: 
Delivered-To: myemail@domain.tld
Received: (qmail 266650 invoked by uid 89); 29 Nov 2020 00:43:58 -0000
Received: from unknown (HELO localhost) (127.0.0.1)
  by localhost.localdomain with SMTP; 29 Nov 2020 00:43:58 -0000
X-DSPAM-Processed: Sat Nov 28 17:43:58 2020
X-DSPAM-Confidence: 0.9899
X-DSPAM-Probability: 0.0000
X-Virus-Scanned: amavisd-new at domain.tld
X-DSPAM-Result: Whitelisted
X-DSPAM-Signature: 1,5fc2eece2666485921812939
Received: from unknown ([127.0.0.1])
        by localhost (mx.domain.tld [127.0.0.1]) (amavisd-new, port 10024)
        with SMTP id kma806hO5pyA; Sat, 28 Nov 2020 17:43:57 -0700 (MST)
Received: from unknown (HELO mx.remotedomain.tld) (xxx.xxx.xxx.xxx)
  by localhost.localdomain with ESMTPS (ECDHE-RSA-AES256-GCM-SHA384 encrypted); 29 Nov 2020 00:43:57 -0000
Received-SPF: none (localhost.localdomain: domain at remotedomain.tld does not designate permitted sender hosts)



 Other spam scanners operable with Amavis

  @spam_scanners = (
    ['CRM114', 'Amavis::SpamControl::ExtProg', 'crm',
      [ qw(-u /var/amavis/home/.crm114 mailreaver.crm
           --dontstore --report_only --stats_only
           --good_threshold=8 --spam_threshold=-8) ],
      mail_body_size_limit => 64000, score_factor => -0.20,
    ],
  );

 Other AV scanners operable with Amavis
  ESET NODE32
  Avast
  Trend Micro
  Kaspersky
  Sophos
  F-Secure
  ...

 Questions, comments, suggestions, corrections...contact Eric on the QMT list