How can I prevent external entity from rejecting emails from a test server?

Question

I am currently working with a client that allows users to generate emails, which are sent to the client's mail server, where they are parsed, content language is added, and they are resent to the recipient.

So, my server basically sends the following:

FROM: sender@myserver.com
TO: receiver@externalclient.com
SUBJECT: hello world
BODY:
|FROM:anyone@anyserver.com|TO:anyoneelse@anyotherserver.com|CC:anycc@anyserver.com|
Dear so-and-so.

Here is the information you were asking for.

Sincerely,

Anyone.

When these emails are sent from our production website (i.e. www.myserver.com) to our SMTP server, they go through without a hitch.

However, when I attempt to send one from our testing websites (i.e. test.myserver.com), they are rejected with the following information:

#5.0.0 smtp; 5.1.0 - Unknown address error 550-'rejecting spoofed message' (delivery attempts: 0)> #SMTP#

Is there any way on our end to get these emails to go through, or do we need to ask the external client to change their configuration to allow us to send emails from other sub-domains?

Answer 1

it has to be the recipient domain to cater the changes.