Email relay
Principle
Our server will forward all emails to another SMTP server. The SMTP server we're gonna install is stupid: only local domain, no account checking, no anti-virus or spam protection.
- From a local point of view, all emails are send using Linux default configuration and system users
- From the other hand - the big SMTP server ("Gmail", "Outlook", ...) - all emails come from the same account
Principle:
As you can see, POSTFIX SMTP server will just act as a proxy between local services and Gmail.
When to use it ?
If you only have a single server and want to monitor it, then use a relay! That's much easier than setup a complete email server. It's also easier to maintain!
Installation
apt-get install postfix mailutils libsasl2-2 ca-certificates libsasl2-modules
Edit Postfix configuration
Set SMTP relay and SASL settings
Create login / password file vim /etc/postfix/sasl_password
Put the following content
[smtp.gmail.com]:587 USERNAME@gmail.com:PASSWORD
Set rights
chmod 640 /etc/postfix/sasl_password
chown postfix:postfix /etc/postfix/sasl_password
Compute new hash for postfix
chown -R postfix /etc/postfix
postmap /etc/postfix/sasl_password
Create TLS policy file
vim /etc/postfix/tls_policy
Put the following content
[smtp.gmail.com]:587 encrypt
Compute new hash for postfix
postmap /etc/postfix/tls_policy
Test you configuration
Check your logs!
cat /var/log/mail.log
You should see something like:
Aug 13 10:15:46 smartcard-gw postfix/pickup[11711]: 558D442DDF: uid=0 from=<root@dev>
Aug 13 10:15:46 smartcard-gw postfix/cleanup[11836]: 558D442DDF: message-id=<20140813081546.558D442DDF@dev>
Aug 13 10:15:46 smartcard-gw postfix/qmgr[11712]: 558D442DDF: from=<root@dev.daxiongmao.eu>, size=361, nrcpt=1 (queue active)
Aug 13 10:15:48 smartcard-gw postfix/smtp[11838]: 558D442DDF: to=<target@domain.com>, relay=smtp.gmail.com[173.194.71.108]:587, delay=2.4, delays=0.02/0.04/0.89/1.5, dsn=2.0.0, status=sent (250 2.0.0 OK 1407917748 n2sm761208lag.18 - gsmtp)
Aug 13 10:15:48 smartcard-gw postfix/qmgr[11712]: 558D442DDF: removed
cat /var/log/mail.err
