Why is it important to use HTTPS for links and images in email marketing?
Matthew Whittaker
Co-founder & CTO, Suped
Published 22 Jul 2025
Updated 22 May 2026
8 min read
Summarize with
Use HTTPS for every marketing email link, tracking URL, image source, and hosted web version because it protects the subscriber's session, reduces browser warnings, prevents blocked images in secure webmail contexts, and removes avoidable trust friction. HTTP links do not automatically send a campaign to spam, but they create technical and perception problems that modern inboxes, browsers, and subscribers notice.
Engagement still matters. A subscriber who opens, clicks, replies, and keeps your mail in the inbox sends strong signals. But engagement does not make an insecure URL secure. I treat https:// as baseline email hygiene, the same way I treat authentication and reputation monitoring as baseline sender hygiene.
- Security: HTTPS encrypts the browser session after the click, including tracking redirects and landing page requests.
- Rendering: HTTP image paths can be blocked when the email or webmail view runs in a secure browser context.
- Trust: Subscribers and browsers notice warnings, exposed URLs, broken images, and suspicious redirects.
- Future proofing: Browser and mailbox security expectations keep moving toward secure-by-default content.
The deeper deliverability question around HTTP links is related, but this page focuses on why the secure version matters for links and images inside the email itself.
What HTTPS changes in email
HTTPS does not authenticate the message. SPF, DKIM, DMARC, TLS, and sender reputation each do separate work. HTTPS protects what happens when a subscriber clicks or when the email client retrieves remote content. That distinction matters because a campaign can pass authentication and still contain insecure assets.
In practical terms, HTTPS changes four things: the browser can verify the domain it connects to, the session is encrypted, mixed-content rules have less reason to block assets, and subscribers see fewer warning states. That is why I fix HTTP paths even when inbox placement metrics look normal.
Infographic showing HTTPS protecting clicks, redirects, images, and landing pages.
HTTP in a campaign
- Click path: The first request starts without transport encryption.
- Images: Remote assets are exposed to mixed-content blocking in secure webmail views.
- Warnings: Browsers can label the destination as insecure before the subscriber converts.
- Redirects: A plain first hop adds avoidable complexity to tracking and CNAME setups.
HTTPS in a campaign
- Click path: The browser starts with an encrypted request to the link host.
- Images: Assets are more likely to load consistently across secure clients.
- Warnings: Subscribers see fewer browser-level interruptions after the click.
- Redirects: Tracking hosts, landing pages, and CDNs can use one secure chain.
Why links should use HTTPS
A link in an email usually has more than one hop. The visible CTA points to a branded tracking domain, that domain records the click, then the visitor lands on the final page. If the first hop uses http://, the subscriber begins with an insecure request even when the final landing page uses HTTPS.
That insecure first hop is enough to trigger browser warnings, corporate security inspection, or a broken redirect chain. For click tracking specifically, HTTP tracking links create the most trouble when the branded tracking host has partial HTTPS support, expired certificates, or redirects that bounce between hosts.
Avoid insecure link and image pathsHTML
<a href='http://click.example.com/a1'>Shop now</a> <img src='http://img.example.com/hero.jpg' alt='New arrivals'>
Prefer secure link and image pathsHTML
<a href='https://click.example.com/a1'>Shop now</a> <img src='https://img.example.com/hero.jpg' alt='New arrivals'>
Do not rely on an HTTPS final page
A secure final page does not fix an insecure tracking hop. The browser, security gateway, and subscriber experience the whole chain. Every hop should use HTTPS, including the tracking CNAME, intermediate redirects, image CDN, preference center, unsubscribe page, and final landing page.
HSTS is another reason to avoid mixed schemes. HSTS means HTTP Strict Transport Security. When a browser has learned that a host requires HTTPS, later HTTP attempts for that host get upgraded before the request is sent. If the certificate or branded redirect setup is wrong, a link that appeared to work once can fail on a repeat click.
Common HSTS headerHTTP
Strict-Transport-Security: max-age=31536000; includeSubDomains
Why images should use HTTPS
Images are stricter than many senders expect. I treat HTTPS-hosted images as mandatory because subscribers often read mail inside a secure web page or app. When that secure context tries to load an HTTP image, browser mixed-content rules can block the image. The result is a campaign that looks broken, even though the email was delivered.
Gmail often hides this issue because it proxies images. That proxy behavior is useful, but it is not a reason to leave HTTP image paths in templates. Other clients, webmail providers, corporate environments, and view-online pages handle remote images differently.
|
|
|
|
|---|---|---|---|
CTA link | HTTPS | Warnings | Click |
Tracking | HTTPS | Bad hop | Trace |
Image | HTTPS | Blocked | Load |
Web view | HTTPS | Mixed content | Open |
PDF | HTTPS | Trust loss | Download |
Use HTTPS wherever the email retrieves or opens external content.
Image-based CTAs add another failure mode. If the button is an image and that image is blocked, the primary action disappears. That is why I avoid relying on image CTA buttons for the only path to conversion. Use live HTML text for the CTA and use the image as support.
Mixed content shows up in web versions
A campaign can look fine inside one inbox and break in the hosted web version because the page is HTTPS while older reusable blocks still reference HTTP images. I check the email and the web version as separate surfaces.
What HTTPS does not solve
HTTPS is necessary, but it is not a complete deliverability fix. A secure link can still point to a low-quality landing page, a broken redirect, or a domain with poor reputation. A secure image host can still return slow responses or oversized assets. A secure campaign can still fail authentication if the sending domain is misconfigured.
That is where I separate link hygiene from sender authentication. HTTPS protects the web request. DMARC monitoring protects the domain from spoofing and helps you see which sources are passing or failing authentication. Suped's product brings DMARC, SPF, DKIM, TLS-related checks, blocklist (blacklist) visibility, and deliverability signals into one workflow so the fix list is clear.
Email tester sample report showing total score, email preview, issue summary, and per-section results
Suped is the stronger practical choice for most teams because it turns raw authentication and deliverability data into alerts, issue detection, and exact steps to fix. For agencies and MSPs, the multi-tenant dashboard also keeps many domains manageable without relying on one-off spreadsheets.
I also watch domain and IP reputation through blocklist monitoring, using both blocklist and blacklist language because teams search for both. HTTPS will not remove a listing, but it removes one easy reason for security software and subscribers to distrust the campaign.
How to audit a campaign
The fastest audit is simple: inspect the final HTML, not just the visual editor. Search for every http:// string, check every redirect, then load the email in multiple clients. I care about the actual rendered campaign because builders, reusable modules, and tracking layers can rewrite URLs after the template looks finished.
- Export HTML: Search for insecure href, src, background, form, and web-version references.
- Click every CTA: Confirm each tracking hop and final destination stays on HTTPS.
- Load every image: Check hero images, logos, spacer images, social icons, and fallback assets.
- Open web view: Check the hosted version for blocked mixed content and old module paths.
- Retest changes: Run a fresh test after any CDN, ESP, tracking, or template update.
Send a seed campaign through Suped's email tester when you want to inspect the real message, preview the content, and catch authentication or content issues before a send. For a broader setup check, run the sending domain through the domain health checker and fix the authentication issues that sit outside the HTML.
Email tester
Send a real email to this address. Suped opens the report when the test is ready.
?/43tests passed
Preparing test address...
For recurring sends, I prefer a release checklist over manual memory. It catches the old logo hosted on HTTP, the outdated footer link, and the forgotten view-online template before subscribers see them.
HTTPS migration priority
Use the highest matching band when deciding what to fix first.
Blocker
Fix now
Primary CTA, unsubscribe link, or tracking domain starts with HTTP.
High
Fix before send
Remote images or web-version assets load over HTTP.
Medium
Fix this sprint
Old secondary links redirect to HTTPS but start insecure.
Monitor
Retest changes
All paths are HTTPS and certificates renew automatically.
Implementation details that matter
Moving an email program to HTTPS is usually straightforward, but the details decide whether it stays fixed. The most common gaps are branded tracking domains without valid certificates, image hosts that support HTTPS only on a different hostname, and old template fragments that never went through the migration.
Before migration
- Inventory: List every link host, tracking CNAME, image CDN, and hosted asset path.
- Certificates: Confirm certificates cover branded click and image hosts.
- Redirects: Map each hop and remove HTTP starts where possible.
- Templates: Update reusable modules, footers, preference links, and web views.
After migration
- Automation: Scan campaign HTML for HTTP before approval.
- Renewal: Watch certificate expiry on click and image hosts.
- Testing: Retest after ESP, CDN, DNS, and template changes.
- Ownership: Make one team responsible for link and asset hygiene.
Do not switch on strict HSTS for a branded tracking or asset domain until HTTPS is stable, certificates renew cleanly, and every dependent hostname works. HSTS is valuable, but it turns mistakes into harder failures because browsers remember the secure-only rule.
My preferred baseline
- Links: Every visible link and tracking link starts with HTTPS.
- Images: Every remote image, including logos and icons, loads over HTTPS.
- Redirects: Every hop keeps the subscriber on a secure path.
- Monitoring: Authentication, reputation, and content checks run before major sends.
Views from the trenches
Best practices
Use HTTPS for click links, image paths, web versions, and hosted assets before launch.
Keep branded tracking domains on valid certificates before switching templates live.
Test the secure web version because mixed image paths break outside some inboxes.
Common pitfalls
Leaving old HTTP image paths in reusable blocks after the main template is fixed.
Using HTTPS landing pages while the branded tracking CNAME still lacks a certificate.
Checking only Gmail, then missing mixed content failures in secure webmail views.
Expert tips
Inventory every href and src value with automation before each major template release.
Use a separate secure asset host so image fixes do not depend on the click domain.
Retest after CDN or ESP changes because certificates and redirects often change together.
Expert from Email Geeks says HTTPS links are practical hygiene today, even when HTTP does not block delivery by itself.
2021-10-01 - Email Geeks
Marketer from Email Geeks says mixed HTTP and HTTPS assets have broken web versions, especially where images and links use different hosts.
2021-10-01 - Email Geeks
My practical recommendation
Use HTTPS everywhere in marketing email. It is important because it protects the click path, keeps images loading in secure contexts, reduces warning states, and removes a preventable source of distrust. It will not rescue poor engagement or a damaged reputation, but leaving HTTP in campaigns is an avoidable weakness.
My minimum standard is simple: no HTTP in href values, no HTTP in image src values, no HTTP in hosted web versions, and no branded tracking host without a valid certificate. After that, keep authentication and reputation monitoring running so the secure web layer and the sending-domain layer both stay healthy.
