Postfix Configuration macOS #

This is a little step-by-step guide which worked for me to send emails from macOS on my local machine.

Step 1 – sasl_passwd file #

Create a SASL (a Simple Authentication and Security Layer) password file:

> sudo vi /etc/postfix/sasl_passwd

The file contains only a single line consisting of the following data:

[mailserver]:[port] [username@domain.com]:[password]

You have to replace [mailserver], [username@domain.com] as well as [password] with the actual data. You might be able to skip the :[port] part.
For example:

smtp.provider.de johndoe@somewhere.de:qwertzuiop

Step 2 – postfix lookup #

Create a postfix lookup for the SASL password file, this is done by executing the following command:

> sudo postmap /etc/postfix/sasl_passwd

You could test this configuration by running:

> postmap -q [mailserver] hash:/etc/postfix/sasl_passwd

This should return your configuration data, continuing the example from above:

> postmap -q smtp.provider.de hash:/etc/postfix/sasl_passwd
johndoe@somewhere.de:qwertzuiop

Step 3 – main configuration #

Now you have to adapt the postfix main configuration file main.cf. I recommend backing it up before you start editing it.

> sudo vi /etc/postfix/main.cf

Some of these settings might be set already, just enter the missing parts at the bottom of the file:

mail_owner = _postfix
setgid_group = _postdrop

# specifix configuration
myhostname = <domain.de>
relayhost = <mailserver>:<port>
smtpd_sender_restrictions = permit_inet_interfaces

# enable SASL
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options =

# enable TLS
smtp_use_tls=yes
smtp_tls_security_level=encrypt
smtp_sasl_mechanism_filter = AUTH LOGIN

# what domains to receive mail for
mydestination =

Step 4 – (re)start postfix #

Now you've to (re)start postfix in order to read in the current configuration:

> sudo postfix start
(or rather) sudo postfix reload

Step 5 – Testing #

It's time to test the configuration by sending a test mail. You could do so by executing:

> date | mail -s testmail recipient@domain.de
> php -r "if (mail('recipient@domain.de', 'postfix test', date('D M d H:i:s T Y'))) { echo 'success'; }"

Step 6 – Mail Queue #

From time to time it's quite useful to have a look at the mail queue:

> mailq

You could reset the mail queue manually by running:

> sudo postsuper -d ALL

Step 7 – Logging #

/var/log/mail.log does not work since macOS Sierra. Apple uses a new log system and does not use the log files / asl any longer.
Now the logs are stored in memory or in a log db.

@see: Server 5.2 missing SMTP Logs

You can use the following command:

> log stream --predicate  '(process == "smtpd") || (process == "smtp")' --info  | grep "to=<"

You can also redirect the output directly into a file:

> log stream --predicate  '(process == "smtpd") || (process == "smtp")' --info > ~/mail.log