Setting up postfix on MacOS High Sierra

MacOS Sierra High comes with preinstalled postfix. Follow these steps to configure it on a local system:

1. Create a sasl_passwd file

sudo nano /etc/postfix/sasl_passwd

• Add this to the file

smtp.gmail.com:587 [email protected]:PASSWORD

Replace EMAIL with your gmail username and replace PASSWORD with your gmail password.

• Create a lookup table

sudo postmap /etc/postfix/sasl_passwd

2. Edit the main.cf file

• Open postfix's main.cf

sudo nano /etc/postfix/main.cf

• Edit these values if they are not set already

mail_owner = _postfix
setgid_group = _postdrop

• Add these fields at the end of the file (I am choosing mtp.gmail.com as myrelayhost to send email from gmail account. You can choose any other SMTP relayhost)

#Gmail SMTP
relayhost=smtp.gmail.com:587
# Enable SASL authentication in the Postfix SMTP client.
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options=noanonymous
smtp_sasl_mechanism_filter=plain
# Enable Transport Layer Security (TLS), i.e. SSL.
smtp_use_tls=yes
smtp_tls_security_level=encrypt
tls_random_source=dev:/dev/urandom

3. Enable less secure app access

If you are using gmail then you must have to enable less secure app access.

4. Set postfix to autorun on reboot

• Disable SIP

• Open /System/Library/LaunchDaemons/com.apple.postfix.master.plist

sudo nano /System/Library/LaunchDaemons/com.apple.postfix.master.plist

• Remove these lines

<string>-e</string>
<string>60</string>

and add these lines

<key>KeepAlive</key>
<true/>

• Reload and relaunch the deamon

sudo launchctl unload /System/Library/LaunchDaemons/com.apple.postfix.master.plist
sudo launchctl load /System/Library/LaunchDaemons/com.apple.postfix.master.plist

• Enable SIP

5. Send mail

Test by sending a mail

echo "Postfix setting test" | mail -s "Hello Postfix" "[email protected]"

Replace [email protected] with the email id of recipent.

Some useful commands

• mailq : Check mails in the queue and errors if mail not sent.
• sudo postfix flush: Flush the queue.
• sudo postsuper -d ALL Delete mails in the queue.
• sudo rm /var/mail/$USER Remove all mails from local host.
• sudo postfix start Start postfix mail system.
• sudo postfix stop Stop postfix mail system.
• sudo postfix reload Reload postfix mail system.

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References:

1. How to send emails from localhost.
2. Postfix auto start on Sierra for smtp relay.