Notes on Linux PostFix email server

Aliases configured in
```
/etc/postfix/virtual
```
compile file in to *.db with postmap
```
/usr/sbin/postmap /etc/postfix/virtual
```

Setup postfix so gmail can send email through your server to use your own domain

Install sasl
- apt install libsasl2-modules sasl2-bin

Tell postfix to use sasldb

# cat /etc/postfix/sasl/smtpd.conf 
pwcheck_method: saslauthd

check that postfix uses config

# postconf -d | grep 'smtpd_sasl_path'
smtpd_sasl_path = smtpd

Debug smtp sasl auth https://wiki.vigor.nz/smtp
add entries to /etc/postfix/sasl_passwd
- then compile to db with # postmap sasl_passwd

Test local user/password with testsaslauthd

# cat /etc/default/saslauthd
  ... MECHANISMS="sasldb
  ... OPTIONS="-c -m /var/spool/postfix/var/run/saslauthd"
# # ls -l /etc/sasldb2   <<The sasldb
# sasldblistusers2
# saslpasswd2 <user>
# testsaslauthd -u <user> -p <password> -f /var/spool/postfix/var/run/saslauthd/mux

Test with openssl s_client

$ echo -n "<user>" | base64
$ echo -n "<password>" | base64
$ openssl s_client -connect vigor.nz:25 -starttls smtp
EHLO test.com
AUTH LOGIN
334 VXNlcm5hbWU6   >> = "Username:" in base64
<user|base64>
334 UGFzc3dvcmQ6   >> = "Password:" in base64
<pass|base64>
535 5.7.8 Error: authentication failed: authentication failure

Configure gmail email

Log into gmail
Click gear top right, Settings, and then all settings
[Accounts and Import] -> [Add another email address]
Popup, complete [Name: <description>] [email: <address>], uncheck [ ][Treat as an alias] then [Next >>].
Complete server details
- SMTP Server: [smtp.vigor.nz] Port: 25
- Username: ["<Normally email address, or smtp user>"]
- Password: ["xxxxxxx"]
- [x] Secure connection TLS
- You should then receive a test email from gmail, and just click on the link or copy the code.

Check tls certificate on smtp server

# echo "quit" | openssl s_client -starttls smtp -crlf -connect <smtp.host>:25 | openssl x509 -noout -text | grep DNS:

Postfix mail queues

Stop mail delivery, add to main.cf
```
defer_transports = smtp
```
monitor q with
```
postqueue -p
```