Configuring Sendmail/postfix?

I am using namecheap privateemail service.

I tried the following and still getting connection refused and I dont know why

Created file /etc/postfix/sasl_passwd

[] username:password
sudo postmap /etc/postfix/sasl_passwd
sudo chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
sudo chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
sudo nano /etc/postfix/
# specify SMTP relay host
relayhost = []: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
sudo service postfix restart

in my maillog I get this:

Nov 24 22:33:34 new-host-1 sendmail[4737]: vAP3XYeD004737:, (48/48), delay=00:00:00, xdelay=00:00:00, mailer=relay, pri=48631, relay=[] [], dsn=4.0.0, stat=Deferred: Connection refused by []

Nov 24 22:36:45 new-host-1 postfix/postmap[4808]: warning: /etc/postfix/sasl_passwd: logical line must not start with whitespace: " [] admin..."