Jeremy Davis's picture

I've finally circled back to test this myself to see if I could reproduce your issue. I launched an unpriveledged LXC container of our v16.1 Observium appliance on Proxmox.

After initial install, within Confconsole, I configured it to use my (personal) SendinBlue account (I created a new SMTP key within the SMTP tab of the SMTP & API section).

Then I tested as per your notes. Here's what I got:

root@jed-test-observium ~# echo "Subject: sendmail test" | sendmail -v jeremy@turnkeylinux.org
Mail Delivery Status Report will be mailed to .
root@jed-test-observium ~# cat /var/mail/root 
From MAILER-DAEMON  Mon Jun  7 05:51:01 2021
Return-Path: <>
X-Original-To: root@observium
Delivered-To: root@observium
Received: by observium (Postfix)
	id C852A142D5; Mon,  7 Jun 2021 05:51:01 +0000 (UTC)
Date: Mon,  7 Jun 2021 05:51:01 +0000 (UTC)
From: MAILER-DAEMON@observium (Mail Delivery System)
Subject: Mail Delivery Status Report
To: root@observium
Auto-Submitted: auto-replied
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
	boundary="AE304141B4.1623045061/observium"
Content-Transfer-Encoding: 8bit
Message-Id: <20210607055101.C852A142D5@observium>

This is a MIME-encapsulated message.

--AE304141B4.1623045061/observium
Content-Description: Notification
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 8bit

This is the mail system at host observium.

Enclosed is the mail delivery report that you requested.

                   The mail system

: delivery via
    smtp-relay.sendinblue.com[34.93.126.74]:587: 250 Message queued as
    <20210607055058.AE304141B4@observium>

--AE304141B4.1623045061/observium
Content-Description: Delivery report
Content-Type: message/delivery-status

Reporting-MTA: dns; observium
X-Postfix-Queue-ID: AE304141B4
X-Postfix-Sender: rfc822; root@observium
Arrival-Date: Mon,  7 Jun 2021 05:50:58 +0000 (UTC)

Final-Recipient: rfc822; jeremy@turnkeylinux.org
Original-Recipient: rfc822;jeremy@turnkeylinux.org
Action: relayed
Status: 2.0.0
Remote-MTA: dns; smtp-relay.sendinblue.com
Diagnostic-Code: smtp; 250 Message queued as
    <20210607055058.AE304141B4@observium>

--AE304141B4.1623045061/observium
Content-Description: Message Headers
Content-Type: text/rfc822-headers
Content-Transfer-Encoding: 8bit

Return-Path: 
Received: by observium (Postfix, from userid 0)
	id AE304141B4; Mon,  7 Jun 2021 05:50:58 +0000 (UTC)
Subject: sendmail test
Message-Id: <20210607055058.AE304141B4@observium>
Date: Mon,  7 Jun 2021 05:50:58 +0000 (UTC)
From: root 

--AE304141B4.1623045061/observium--

And not only did the test appear to work correctly within my server; the test email arrived in my inbox too!

So I'm a bit unsure why my experience was so radically different to yours?!

Could you please confirm which version your appliance is? If you're not sure, please post the output of:

turnkey-version

The only other thing that occurs to me is that perhaps there have been some config and/or package changes that have broken postfix in your appliance? Perhaps it's worth migrating to a new appliance? Let me know if this is an option for you and I can give you some adive on the easy way to do that.