SMTP Relay Solution Via Provider

Not sure if this is the best place to post this issue…but I’ll try:

In the context of kopano installations, I have read about
"SMTP Relay Solutions via Provider"
There are great posts from Andreas about that.

Before I am going to install a Kopano server for my big family, I would like to understand a few things.

So far, I see the these steps required:

so far, so good…

The domain “” is hosted at myISP, where I am getting the SMTP access credentials from, before adding them to the postfix smtp_auth file.

Now some questions:

  1. Is it possible to add further smtp accounts, also of other domains?
    So, do I need to do these smtp_auth entries for ALL users using other domains (,,…)?

  2. What exactly has changed after restarting the postfix module with the newly configured amtp_auth file?

  3. Does it have any infulence on how the sender email address appears for the recipient?

  4. Does it mean that sending emails out of Kopano as or, always appear at the recipient with the sender address ""?

I hope I could explain my questions well enough…
I am aware of the spam-topic, so a professionally hosted ISP mail server (blacklists, SPF, etc) are certainly a good choice in such a setup.


Hi Thomas,
what are you planning in general?
Will the Kopano server be at your home or on a virtual machine at the internet?
As far as I understand - the MX should point to your provider and kopano server will collect mails from several other accounts?
Which post from Andreas did you mean?
Best regards

Hello Merlin,

I was referring to this article:
where Andreas is partly pointing out how to make use of an SMTP relay, so I asked here for more details.

Kopano will run on my own physical server.
The users (partly) already have their email addresses, which I would like to use for their Kopano accounts (actually, they do not want to change their existing email accounts), as pointed out in the exampes above.


Hi @ThomasB ,
do you have experience with Linux and postfix?
Looks like with postfix it’s possible:
If your server is at home, ensure you have at least VDSL connection and a dyndns Service.

best regards

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