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What is this?

MTA-STS (Mail Transfer Agent Strict Transport Security) is a standard that forces other mail servers to use encrypted TLS connections when delivering email to your domain. Without it, a network attacker could silently strip TLS from email in transit.

Why does it matter?

Email is delivered between servers using SMTP. By default, SMTP tries TLS but falls back to plaintext if TLS is not available — a downgrade attack. MTA-STS prevents this fallback, ensuring all email delivered to your domain is encrypted in transit.

How to fix it

Implementing MTA-STS requires two things: 1. A DNS TXT record at _mta-sts.yourdomain.com: v=STSv1; id=20240101001 2. A policy file hosted at: https://mta-sts.yourdomain.com/.well-known/mta-sts.txt Policy file content: version: STSv1 mode: enforce mx: mail.yourdomain.com max_age: 86400 Start with mode: testing to see reports before enforcing. Use mta-sts.io for a guided setup.

What is this?

An HTTP to HTTPS redirect automatically sends visitors who type http:// (or click an old link) to the secure https:// version of your site.

Why does it matter?

If HTTP is not redirected, some visitors may unknowingly browse your site without encryption. It also causes duplicate content issues for SEO since the same page exists on both http:// and https://.

How to fix it

Add a 301 redirect in your server config: Nginx: return 301 https://$host$request_uri; Apache: Redirect permanent / https://yourdomain.com/ Or in .htaccess: RewriteEngine On RewriteCond %{HTTPS} off RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

What is this?

HTTP Strict Transport Security (HSTS) is a response header that tells browsers to only ever connect to your site over HTTPS — even if the user types http:// or clicks an http:// link. The browser enforces this locally for the duration of max-age.

Why does it matter?

Even with an HTTP redirect in place, the very first request could go over HTTP before being redirected. A network attacker could intercept that first request (SSL stripping attack). HSTS prevents this by making the browser upgrade to HTTPS before making any request.

How to fix it

Add this header to your HTTPS responses: Strict-Transport-Security: max-age=31536000; includeSubDomains Nginx: add_header Strict-Transport-Security "max-age=31536000; includeSubDomains" always; Apache: Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains" Only add HSTS after you are certain your entire site works over HTTPS, including all subdomains if you use includeSubDomains.

What is this?

Content Security Policy (CSP) is a browser security feature that lets you control which resources (scripts, styles, images, fonts) a page is allowed to load, and from which origins.

Why does it matter?

CSP is one of the most effective defences against Cross-Site Scripting (XSS) attacks. Without CSP, an attacker who injects malicious JavaScript into your page can load resources from anywhere, steal session cookies, or redirect users.

How to fix it

Add a Content-Security-Policy header. Start with a report-only policy to detect issues without breaking anything: Content-Security-Policy-Report-Only: default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; Once tested, switch to enforcing: Content-Security-Policy: default-src 'self'; ... CSP policies can be complex for sites with third-party scripts. Use https://csp-evaluator.withgoogle.com/ to evaluate your policy.

What is this?

robots.txt is a plain text file at the root of your website that tells search engine crawlers which pages they are and aren't allowed to index.

Why does it matter?

Without a robots.txt, crawlers may index admin panels, staging areas, duplicate content, or other pages that should not appear in search results. A well-configured robots.txt also prevents crawl budget waste on unimportant pages.

How to fix it

Create a file at https://yourdomain.com/robots.txt with at minimum: User-agent: * Disallow: Sitemap: https://yourdomain.com/sitemap.xml To block specific paths: User-agent: * Disallow: /admin/ Disallow: /private/ Allow: / WordPress: generated automatically. Check Settings > Reading. Laravel: create public/robots.txt manually.

What is this?

An XML sitemap is a file that lists all the important URLs on your website, helping search engines discover and index your pages more efficiently.

Why does it matter?

Search engines may miss pages that are not linked from anywhere (orphan pages) or pages deep in your site structure. A sitemap ensures they are found and indexed. It also allows you to signal content priority and update frequency.

How to fix it

Create an XML sitemap at https://yourdomain.com/sitemap.xml WordPress: install Yoast SEO or use the built-in sitemap at /wp-sitemap.xml Laravel: use spatie/laravel-sitemap package Static sites: generate with a sitemap generator tool After creating your sitemap, submit it to: - Google Search Console: search.google.com/search-console - Bing Webmaster Tools: bing.com/webmasters Also reference it in your robots.txt: Sitemap: https://yourdomain.com/sitemap.xml