postconf

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Postfix sends and receives e-mail with SMTP (port 25, submission 587). On servers it is often only a relay: local programs (cron, monitoring, apps) send mail through Postfix to a smart host (Microsoft 365, SendGrid, Amazon SES, Hostinger SMTP) with TLS and a login. Settings are in main.cf (postconf edits them safely) and services in master.cf.

For your own domain you also need SPF, DKIM and DMARC DNS records, or your mail lands in spam.

طريقة الكتابة

postconf [-n] [-e 'key = value'] [KEY]
postqueue -p | -f ; postsuper -d ID|ALL

الأجزاء الرئيسية

Tools

postconf -n: Show only changed settings.
postconf KEY: Show one setting.
postconf -e 'KEY = VALUE': Change a setting.
postqueue -p (mailq): Show the queue.
postqueue -f: Try to send all queued mail now.
postsuper -d ID / -d ALL: Delete mail from the queue.
postcat -q ID: Show a queued mail.
postfix check / reload: Check config / reload.
postmap FILE: Build lookup tables (sasl_passwd, transport).

الخيارات 7

الأكثر استخدامًا

Important main.cf settings

myhostname / mydomain: Server and domain name.
inet_interfaces = loopback-only: Accept mail only from this host (relay setup).
relayhost = [smtp.example.com]:587: Smart host.
smtp_tls_security_level = encrypt: Always use TLS outbound.
smtp_sasl_auth_enable = yes: Log in to the smart host.
smtpd_tls_cert_file / smtpd_tls_key_file: Certificate for incoming TLS.
mynetworks: Hosts allowed to relay (keep it small!).

أمثلة 10

$ مستخدم عادي# بصلاحية root (أو مع sudo)

1Install and send only from this host

#dnf install -y postfix s-nail cyrus-sasl-plain
#postconf -e 'inet_interfaces = loopback-only'
#systemctl enable --now postfix

2Relay through a smart host with TLS and login

#postconf -e 'relayhost = [smtp.example.com]:587' 'smtp_tls_security_level = encrypt' 'smtp_sasl_auth_enable = yes' 'smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd' 'smtp_sasl_security_options = noanonymous'
#echo '[smtp.example.com]:587 alerts@example.com:Example-Only-Pass' > /etc/postfix/sasl_passwd
#chmod 600 /etc/postfix/sasl_passwd && postmap /etc/postfix/sasl_passwd
#systemctl reload postfix

3Send a test mail

$echo "Test from $(hostname)" | mail -s "Postfix test" ops@example.com
#journalctl -u postfix -n 20

4Look at the queue

#postqueue -p
#postcat -q 4F2A91C0D1
#postqueue -f

5Clean the queue

#postsuper -d 4F2A91C0D1
#postsuper -d ALL deferred

6See your changed settings
```
#postconf -n
```
7Check the config
```
#postfix check
```

8Check SPF, DKIM and DMARC of a domain

$dig +short TXT example.com | grep spf
$dig +short TXT default._domainkey.example.com
$dig +short TXT _dmarc.example.com

9Test TLS of a mail server

$openssl s_client -connect mail.example.com:25 -starttls smtp </dev/null 2>/dev/null | grep -E "subject|issuer|Protocol"

10Find why a mail was not sent

#grep "status=deferred\|status=bounced" /var/log/maillog | tail -5
#journalctl -u postfix --since "1 hour ago" | grep -E "status=(deferred|bounced)"

انتبه

Never be an open relay: keep mynetworks small and inet_interfaces = loopback-only on app servers.
Many clouds (Azure, AWS) block outbound port 25 — use 587 to a relay service.
sasl_passwd contains a password: rights 600, and do not commit it.

الملفات

/etc/postfix/main.cf: Main settings.
/etc/postfix/master.cf: Services and ports.
/var/spool/postfix/: Queue.
/var/log/maillog or journal: Logs.

نصائح للحفظ

Send monitoring and cron mails through one relay host, so only one server needs SMTP credentials.

رموز الخروج

`0`	Success.
`1`	Error.

`postconf`

ماذا يفعل

طريقة الكتابة

الأجزاء الرئيسية

Tools

الخيارات 7

Important main.cf settings

أمثلة 10

1Install and send only from this host

2Relay through a smart host with TLS and login

3Send a test mail

4Look at the queue

5Clean the queue

6See your changed settings

7Check the config

8Check SPF, DKIM and DMARC of a domain

9Test TLS of a mail server

10Find why a mail was not sent

انتبه

الملفات

نصائح للحفظ

رموز الخروج

الدليل الكامل

ماذا يفعل

طريقة الكتابة

الأجزاء الرئيسية

Tools

الخيارات 7

Important main.cf settings

أمثلة 10

1Install and send only from this host

2Relay through a smart host with TLS and login

3Send a test mail

4Look at the queue

5Clean the queue

6See your changed settings

7Check the config

8Check SPF, DKIM and DMARC of a domain

9Test TLS of a mail server

10Find why a mail was not sent

انتبه

الملفات

نصائح للحفظ

رموز الخروج

أوامر مرتبطة

مُستخدم في هذه الدروس

الدليل الكامل

`postconf`