Postal is an open source SMTP server. Postal versions less than 3.3.5 had a HTML injection vulnerability that allowed unescaped data to be included in the admin interface. The primary way for unescaped data to be added is via the API's "send/raw" method. This could allow arbitrary HTML to be injected in to the page which may modify the page in a misleading way or allow for unauthorised javascript to be executed. Fixed in 3.3.5 and higher.