After migrating my postfix mailserver I had problems with my localhost satellite/smarthost system.
I had a filled up postfix queue and lots of logs with “SASL PLAIN authentication failed”.
I remembered that I updated the user password during migrating the remote postfix server so i tried updating the passwords in my /etc/postfix/sasl_password file – didn’t help.
Solution
I also had to recreate the hashmap for the passwords:
sudo postmap hash:/etc/postfix/sasl_password