HSTS - Browser HTTPS Only

   The HTTP Strict-Transport-Security response header (often abbreviated as HSTS) lets a web site tell browsers that it should only be accessed using HTTPS, instead of using HTTP for 604800 seconds

X-Cache HTTP Header

   The resource was not in the website cache, and was pulled from the origin server like Varnish servers.

Character Encoding :utf-8

   This website is using utf-8 character encoding in HTML , character encoding is used to represent a repertoire of characters by some kind of encoding system.

SPF

   The Sender Policy Framework (SPF) is an email-authentication technique which is used to prevent spammers from sending messages on behalf of your domain. With SPF an organisation can publish authorized mail servers.

SendGrid

   SendGrid is a Denver, Colorado-based customer communication platform for transactional and marketing email.

Varnish

   Varnish is an HTTP accelerator designed for content-heavy dynamic web sites as well as APIs. In contrast to other web accelerators, such as Squid, which began life as a client-side cache, or Apache and nginx, which are primarily origin servers, Varnish was designed as an HTTP accelerator.

Server partial requests support

   The Accept-Ranges response HTTP header is a marker used by the server to advertise its support of partial requests. The value of this field indicates the unit that can be used to define a range.