We have a Drupal website on a Linux server, it is using mail() to send mail through PHP. I think that would be using PHPmailer and sendmail.

Domain is www.myclientdomain.com and we can receive email from the website all day long. To our email, to our Gmail, everything is great.

However, they cannot receive any email from the web server. Email is being sent as no-reply@myclientdomain.com 

They are running Exchange I believe and we have an SPF record in place but that doesn't seem to be helping at all.

How can I best simulate sending an email from the server, and testing what their mail server is responding with. What tools can I use to see some logs, or get to the root of this issue? I am not getting much help from their Exchange admin, doesn't appear that it is ever hitting their Exchange so something before it may be squashing it.. Barracuda, who knows.