Install sasl:
yum install cyrus-sasl-plain -y
Install Postfix with the following command:
yum install postfix
Open or create the /etc/postfix/sasl_passwd file, using your favorite text editor
vi /etc/postfix/sasl_passwd
modify with the following
[mail.isp.example]:587 username:password
create the hashed file with the following command
postmap /etc/postfix/sasl_passwd
give the right permissions
chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
Open the /etc/postfix/main.cf file with your favorite text editor:
vi /etc/postfix/main.cf/etc/postfix/main.cf
Do the following changes:
# specify SMTP relay host [mail.isp.example]:587 # enable SASL authentication smtp_sasl_auth_enable = yes # disallow methods that allow anonymous authentication. smtp_sasl_security_options = noanonymous # where to find sasl_passwd smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd # Enable STARTTLS encryption smtp_use_tls = yes # where to find CA certificates smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
restart the Postifix server issuing a
service postfix restart