====== Relay to external SMTP server ======

[[https://www.linode.com/docs/email/postfix/postfix-smtp-debian7/|Configure Postfix to Send Mail Using an External SMTP Server]]

===== Simple postfix configuration script =====

<code bash>
apt-get install postfix bsd-mailx
wget https://raw.githubusercontent.com/Tontonjo/proxmox_toolbox/main/proxmox_toolbox.sh
bash proxmox_toolbox.sh
</code>


For TLS on port 465 add followin config lines:
<code bash>
postconf smtp_tls_wrappermode = yes
postconf smtp_tls_security_level = encrypt
</code>




===== Manual configuration =====

<file |/etc/postfix/relay_by_sender>
# Specify zero or more "type:name" lookup tables. Type is a service defined in master.cf
cloudservice@example.org    [smtp.gmail.com]:587
</file>
cd /etc/postfix && postmap relay_by_sender

<file | /etc/postfix/sasl_passwd>
[smtp.gmail.com]:587  myrealsender@gmail.com:secret_password
</file>

<code bash>
cd /etc/postfix && postmap sasl_passwd
sudo chown root:root /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
sudo chmod 0600 /etc/postfix/sasl_passwd /etc/postfix/sasl_passwd.db
</code>

<file | main.cf>
...
# A sender-dependent override for the global relayhost parameter setting
sender_dependent_relayhost_maps = hash:/etc/postfix/relay_by_sender
smtp_sender_dependent_authentication = yes
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_sasl_security_options = noanonymous
</file>


<code bash>service postfix restart</code>

Test email:
<code bash>cat /etc/issue | mailx -r "cloudservice@example.org" -s "test relaya" "destination@email.org"</code>

====== Issues ======

(SASL authentication failed; cannot authenticate to server smtp.server.org[11.22.33.44]: no mechanism available)
solution: smtp_sasl_security_options = noanonymous