Postfix Mail Relay Server with HA for ISP

kryspek · 04-19-2017, 05:33 AM

Hello,
I'm completely new to this whole story with Relay servers, I've been given task to set up Open source relay server with high authority. The scenario is:
Isp that im currently working with wants a separate server to forward emails to it's destination. Mainly used for printers etc to send out notifications to users. Mail server is currently set up on a different server, running office 365. It has to be an Open Relay, I've been looking through many sources and still can't get the whole understanding of it.

My question is how to set up Postfix on Ubuntu to act as ONLY open relay server on a separate server, and from my understanding how to point the Server 1 Office 365 to send mail through the relay server, which then will deliver mail to it's destination. I know Open relay is bad for spammers, but i believe there's settings in postfix to allow what networks are allowed to relay emails through it.

Need more information? Feel free to ask me!
Thanks for help!

TenTenths · 04-19-2017, 07:46 AM

So what have you tried so far?

Habitual · 04-19-2017, 09:20 AM

Quote:

Originally Posted by kryspek

My question is how to set up Postfix on Ubuntu to act as ONLY open relay server on a separate server, and from my understanding how to point the Server 1 Office 365 to send mail through the relay server, which then will deliver mail to it's destination. I know Open relay is bad for spammers, but i believe there's settings in postfix to allow what networks are allowed to relay emails through it.

https://help.ubuntu.com/community/Postfix < -- start here.

Ask away.

kryspek · 04-19-2017, 09:54 AM

Quote:

Originally Posted by Habitual

https://help.ubuntu.com/community/Postfix < -- start here.

Ask away.

Thank you very much for this link! Haven't came across it yet! It will come in very handy!

Iv'e set up before Postfix to relay email through gmail, with spamassassin and GUI Webmin to try understand this whole thing, I've came across this page also, https://nacko.net/creating-an-outgoi...-spamassassin/

Quote:

7) Later on, we’ll be setting up some real email addresses to map to virtual host names. To prepare for this, add this line to the end of the file.
virtual_alias_maps = hash:/etc/postfix/virtual

In /etc/postfix/virtual, we want to define our real email addresses. We recommend setting up at least these three.
postmaster admin@yourdomain.com
abuse admin@yourdomain.com
root admin@yourdomain.com

I'm struggling to understand this part, any other tutorial i have read, always specified relayhost = and then specified the login and the password for that email service, and in this tutorial above he doesn't do anything like that but does Virtual Host Maps where any other previous tutorial hasn't. Also have been chatting with my coli and said i won't be touching the main server where the SMTP is located, which it put me off tracks, because i thought i will have to provide some sort of login and password from that mail server into the second server which is the Relay Server.
Thanks!

//Edit

What domains to receive mail for <-- Virtual maps?
If thats the case how to configure Virtual Alias Maps to accept any email form any user on any domain?
Thanks

Habitual · 04-19-2017, 11:13 AM

Here's what I suggest:
Read twice the Configuration section at https://help.ubuntu.com/community/Postfix#Configuration
Relay_host values can be compared to a working host's configuration using

Code:

postconf -d

on an existing postfix server.

I don't have the focus right now for this, sorry.
Here's some self-paced instruction material.
https://www.google.com/search?q=postfix+to+office+365

Using Office 365 as a Smart Host with Postfix

Good Luck.

TB0ne · 04-23-2017, 08:24 AM

Quote:

Originally Posted by kryspek

Thank you very much for this link! Haven't came across it yet! It will come in very handy!
Iv'e set up before Postfix to relay email through gmail, with spamassassin and GUI Webmin to try understand this whole thing, I've came across this page also, https://nacko.net/creating-an-outgoi...-spamassassin/

I'm struggling to understand this part, any other tutorial i have read, always specified relayhost = and then specified the login and the password for that email service, and in this tutorial above he doesn't do anything like that but does Virtual Host Maps where any other previous tutorial hasn't. Also have been chatting with my coli and said i won't be touching the main server where the SMTP is located, which it put me off tracks, because i thought i will have to provide some sort of login and password from that mail server into the second server which is the Relay Server.

//Edit

What domains to receive mail for <-- Virtual maps? If thats the case how to configure Virtual Alias Maps to accept any email form any user on any domain?

Don't know why you're doing anything with virtual alias maps or anything else. If you want an open relay, a basic install of Postfix gets you 90% there. The documentation (that you were linked to before), tells you how to do this: http://www.postfix.org/BASIC_CONFIGU...tml#relay_from

Put whatever networks/addresses you want to relay mail for into the mynetworks line in main.cf, either for whole subnets or individual hosts...it explains both.

schnappi · 04-25-2017, 12:04 PM

Postfix relay:

Append postfix/main.cf with (ignore three smtp_sasl options if want open relay)

[CODE]

Code:

relayhost = smtp-relay-server.hostname:port
smtp_sasl_auth_enable = yes
smtp_sasl_security_options = noanonymous
smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
smtp_use_tls = yes
smtpd_tls_cert_file= file
smtpd_tls_key_file= file
smtp_tls_CAfile = file

Create/ edit postfix/sasl_passwd (if want authentication) with

Code:

smtp-relay-server.hostname:port username:password

Run

Code:

postmap postfix/sasl_passwd

&

Code:

service postfix restart