One of my yunohost server has been blacklisted by free for several days, Free blacklist email server if there is a big variation of email sent.
In this tuto, I explain how I have used an other yunohost server to relay my mails to Free.
Server A: is the blacklisted server
Server B: The future relay
On Server B
Create a smtp account
Add the domain to yunohost
yunohost domain add YOURDOMAIN.TLD
Create a user with a strong password
yunohost user create relay -f RELAY -l RELAY -m relay@YOURDOMAIN.TLD -p PASSWORD -q 0
Copy dkim key
Take the dkim key in Server A and copy it in Server B
Dkim keys are in /etc/dkim
On Server A
Configure SASL authentication
cd /etc/postfix
echo "SERVER_B.YOURDOMAIN.TLD relay:PASSWORD" > sasl_passwd
postmap sasl_passwd
chmod go=--- sasl_passwd
chmod go=--- sasl_passwd.db
Add a transport file
cd /etc/postfix
echo "free.fr smtp:SERVER_B.YOURDOMAIN.TLD" > transport
echo "aliceadsl.fr smtp:SERVER_B.YOURDOMAIN.TLD" > transport
postmap transport
echo "transport_maps = hash:/etc/postfix/transport" > main.cf
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
Restart postfix
service postfix restart
Test
To test you can check the log file on each server:
tail -f /var/log/mail.log