ATS is using Joomla!'s JMailer to send out its emails. This means that the sender name and email address are those specified in the global configuration of your site. I was about to tell you that this is the end of the story, however it just dawned to me that you can abuse a different ATS feature to do exactly what you want!
Indeed, you can trick ATS into reporting a different from email address using a seemingly unrelated feature. Each support category has the "Category email" option. Set it to the no-reply email address you have created. As you can see in plugins/ats/postemail/postemail.php around line 400 when this is not empty it's overriding the "From email" defined in your site's global configuration, therefore the emails sent out to your users appear to be coming from this email address.
Normally this feature is used for the "reply by email" feature in ATS but you can safely abuse it as I described to do exactly what you want. Cool, huh? :)
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
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