Enabling "Allow Header Spoofing" allows email to be sent via the SMTP setup in that address..If you want to use an email address to be able to send or receive mail.... you would configure it in osTicket.So if you want to send or receive mail using primary@example.com, alias1@example.com, and alias2@example.com then you need to set them up.As an example if I wanted to setup a faux@company.com in osTicket, but I dont want to setup SMTP settings for this address. . Allowing spoofing on another address means that osTicket will attempt to spoof the email hgeaders when sending an email so that it can use a non-existent or aliased email address as the FROM address.