How to send email from MiaB using an external SMTP relay

I am creating this post simply to have an easily searched post with a link to a how-to to accomplish this. The question has been asked here before but a clear answer has never been posted. Thanks to @murgero for posting this link in another topic. :slight_smile:

Of course all of the steps in that linked article are not necessary - I have not gone through it step by step to determine the exact steps required.

And most importantly, keep in mind that this is an unsupported modification meaning that when you upgrade your Mail-in-a-Box to a newer version, these steps must be repeated as the changes will be overwritten.


The steps will need to be reproduced when a new domain is added to the box as well. I think the postfix configuration file is overwritten with that too.

Where is the link to the article?

Start where the instructions say:

Configuring SMTP Usernames and Passwords

In this tutorial one should read under General type of mail configuration. Select the item Internet Site, but here you should select Satellite System. Which one is right?

Would someone maybe so nice and explains everything step by step, install from Postfix or configure to edit etc.
for example what happens to the other entries in should they be removed or remain unchanged?

The first is sending from MiaB using a relay … the second is using MiaB as a relay for another mail server. The two different articles describe two completely different things. Which are admittedly, very similar.

thanks for the education.
I have another server and would like to equip it with Postfix to send and receive emails. Alias and DNS are already set up on my MIAB server, how should the look from the other server to send and receive emails?

Looking to do the same, my question is:
We need to create a few files to do so /etc/postfix/sasl_passwd and /etc/postfix/sasl_passwd.db as well as modify /etc/postfix/
Will the sasl_passwd files be deleted when MIAB updates? If not, should be as simple as running a script to add the required lines to after a MIAB update, correct?

I am curious about this too. Could somebody explain how do we setup a satellite system forwarding to an existing server?

A - primary
B - satellite (with a different domain)
Can B forward to A via port 587 and then A send to the destination via port 25?

I run AnyMXRelay SMTP relay and I can tell you that the answer is no. As a matter of fact in the 5 years or so I have been running this service there has been only one time where an upgrade of Mail-in-a-Box affected anything with the relay.

The problem with AnyMXRelay SMTP relay is it is IPv4 only based on a simple test on your domain name, anydomain. Both MX records for anydomain also do not have AAAA records. This means AnyMXRelay is not much different from PostMarkApp or SparkPostMail as they are IPv4 only.

A good IPv6 compatible SMTP relay is GMAIL SMTP or Migadu SMTP.

Which is actually irrelevant as the service is using the domain,, not

However, that said, since IPv6 adoption is relatively weak amongst email providers, our upstream provider has chosen to not add the complexity of IPv6 as you are not going to find an IPv6 only email server in production, except for amongst hobbyists.

I have, and I will continue to push for IPv6 adoption, but really, at this point in time, it is not relevant to the masses.

The underlying server handling AnyMXRelay will be migrated to new hardware sometime in the next 4 months, so I will push as hard as possible for IPv6 to be enabled at that time.

Thank you for pledging to convert AnyMXRelay SMTP to IPv6 in 4 months. If that happens, I will recommend customers to you.