There's a closed post about this topic, so I cannot reply in that thread.

I'm supporting a client who uses LS version 2.73.0 build 171219.

I need a way to configure a  separate Send from and Reply to email addresses due to a corporate policy for how email must be sent and replied to (to avoid spoofing filters). 

They have asked if I configure things so the email in invitations and reminders is reply-to their actually email, but the sent-from email address be from a subdomain of their organization. 

As they are using their own instance, I'm wondering if someone can point me to the php file and line of code where I can address this requirement?