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Set up Postfix to send through SMTPeter

Configure your hostname

Before you can properly relay your email messages, make sure that the myhostname parameter is configured with your server's fully-qualified domain name (FQDN). You can set this by going to /etc/postfix/main.cf and set the following:

myhostname = fqdn.yourdomain.com

Configure SMTP username and password

The next step is to configure your SMTP username and password for SMTPeter. These credentials are generally stored in a file called sasl_passwd in your /etc/postfix/ directory. If you already have the sasl_passwd file, open it using your text editor of choice:

$ sudo nano /etc/postfix/sasl_passwd

If not, simply create one. On a new line, add the following (replacing username and password with your SMTPeter SMTP credentials):

[mail.smtpeter.com] USERNAME:PASSWORD

If you want to specify the port, you can do so by adding the port number after the hostname:

[mail.smtpeter.com]:587 USERNAME:PASSWORD

When you add (or change) these credentials you should run the following postmap command:

$ postmap /etc/postfix/sasl_passwd

For security reasons, run the following command to make sure only root can read and write to the file with your SMTP credentials: 

$ sudo chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db

Configure Postfix to send all email through SMTPeter

Now you have set up your credentials it is time to configure Postfix to use SMTPeter. First open your Postfix configuration file, /etc/postfix/main.cf, with your text editor of choice:

$ sudo nano /etc/postfix/main.cf

Then update or add the following configuration settings:

# enable SASL authentication
smtp_sasl_auth_enable       = yes

# tell Postfix where the credentials are stored
smtp_sasl_password_maps     = hash:/etc/postfix/sasl_passwd 
smtp_sasl_security_options  = noanonymous

# use STARTTLS for encryption
smtp_use_tls                = yes 

# specify SMTP relay host
relayhost                   = [mail.smtpeter.com]:587

# where to find CA certificates
smtp_tls_CAfile             = /etc/ssl/certs/ca-certificates.crt

Note: If you specified a non-default TCP port in the *sasl_passwd file, you will have to use the same port when setting the relayhost parameter.

After you have saved your changes, restart Postfix and you should be ready to test. 

$ sudo service postfix restart

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