sudo apt-get install opensmtpd

wget https://www.opensmtpd.org/archives/opensmtpd-portable-latest.tar.gz
tar -xzf opensmtpd-portable-latest.tar.gz

./configure
make
sudo make install

makemap smtpd_remote

smtpctl encrypt

accept for local alias <aliases> deliver to mbox

accept from any for domain 'example.org' virtual <virtusers> deliver to mbox

makemap -t aliases aliases
makemap -t aliases virtusers

table aliases db:/etc/aliases.db
table virtusers db:/etc/virtusers.db

max     max
moritz  moritz@example.com

makemap -t aliases users
table users db:/etc/users.db
table domains '/etc/domains'
accept from any for domain <domains> virtual <users> deliver to mbox

accept from local for any relay

accept from local for any relay via secure+auth://provider@mail.provider.com:25 auth <authtable>

provider Username:Password

accept from source 10.0.0.0/24 for any relay

queue encryption key [Key]

openssl rand -hex 16

queue compression

max-message-size 20M

openssl s_client -starttls smtp -connect mail.example.org:587 -crlf

perl -MMIME:Base64 -e 'print encode_base64("\000Username\000Password");'

clamsmtpd -f /etc/clamav/clamsmtpd_in.conf
clamsmtpd -f /etc/clamav/clamsmtpd_out.conf