Software should never be using -f with user emails, regardless if it's sanitized or not. -f sets the return path, which will trigger DMARC protection if the dom

Software should never be using -f with user emails, regardless if it's sanitized or not. -f sets the return path, which will trigger DMARC protection if the domain doesn't allow it. For example, the yahoo.com policy will reject all mail if you try to set the return path to the user's yahoo.com address using -f. The best way I've found to send mail on behalf of someone else is to leave the return path (-f) and From header pointing to your own domain, and use the Reply-To header with the users email.