Domain masking makes a cold email sending domain show your real website while the address bar stays on the sending domain. It works, but for most outreach domains a clean 301 redirect to your main site over HTTPS is the simpler and safer default. Our research on sending-domain redirects found that, for one major URI blocklist, the web address a domain resolves to mattered more than what the page shows. Masking doesn't change that address. What helps is a clean redirect hosted somewhere that isn't crowded with outreach domains. Below: what masking is, how it compares with a redirect, what we measured, and the setup we recommend.
Cold email runs on secondary domains. getacme.com and tryacme.com carry the outreach so acme.com stays protected. When a prospect types one of them into a browser, it should lead to the real company, not a blank or parked page. There are two common ways to do that: domain masking and a redirect. There are plenty of opinions on which is better, and plenty of smart people in cold email have tested both. We did our own research on the part that affects deliverability. This is what we found.
What domain masking is
Domain masking (also called masked forwarding or frame forwarding) shows your main website's content on the sending domain, and the address bar keeps showing the sending domain. It's usually done one of two ways:
- Frame-based masking. The sending domain serves a small page that loads your main site inside a full-page frame. Many registrars offer this as a "forwarding with masking" option.
- Proxy-based masking. A server fetches your main site and serves it again under the sending domain, so the content looks native to it.
A redirect does something simpler: the sending domain answers with a 301 Moved Permanently and the browser goes to your main site. The address bar changes to your main domain.
Domain masking vs a 301 redirect
| Domain masking | 301 redirect | |
|---|---|---|
| Address bar | Stays on the sending domain | Changes to your main domain |
| What search engines see | A frame with no content of its own, or a copy of your site on a second domain | A clear signal that your main domain is the original |
| When it breaks | Frame masking shows a blank page if your site forbids framing (the X-Frame-Options or frame-ancestors security headers, which many sites send by default) | Only if the server answering for the sending domain is down |
| HTTPS | The sending domain needs its own certificate, and a proxy must also handle your site's assets and links | The sending domain needs a certificate for the redirect hop only |
| Blocklist grouping | Depends on the web address the sending domain resolves to | Depends on the web address the sending domain resolves to |
The last row is the one that matters for deliverability, and it's the same for both. Which brings us to the research.
How a sending-domain redirect works
Three things happen when someone visits a sending domain:
- DNS lookup. The domain's A record returns the IP address of the web server that answers for it.
- A secure connection. The browser connects to that address and checks the domain's TLS certificate.
- The response. For a redirect, the server replies with a status code, ideally
301 Moved Permanently, and the address of your main site. For masking, it replies with the framed or proxied page.
Anyone can repeat step one for any domain. That means the address your sending domain resolves to is public, and so is every other domain that resolves to the same place.
Why the hosting address matters
Redirects and masked pages in cold email are usually served by a small number of web servers run by the infrastructure provider, so large numbers of unrelated outreach domains end up on the same few addresses. That makes them easy to group together.
Some blocklists use exactly that kind of relationship. When several domains on one address are listed, the others on it can start to look like part of the same activity. A well-run domain can be judged partly by its neighbours. The fix isn't changing what the page shows, masked or not. It's changing where it lives.
What we measured
We track blocklist signals across the domains on our platform, and redirects gave us a clean way to test the question: the way redirect addresses had been assigned to domains was effectively random, so if the address made no difference, listing rates would look the same everywhere once you account for who owns each domain. They didn't.
- For one of the major URI blocklists, the address mattered. Domains that shared an address with already-listed domains were listed noticeably more often, even compared with other domains owned by the same customer.
- Other major domain blocklists didn't show the pattern. Their listings followed the domain and how it was used.
- Page content didn't change categorisation. In our checks with a large web-filtering vendor, redirect domains didn't take on their destination site's category. Categorisation followed sending behaviour, not the website.
We didn't test masked domains separately. But the third finding is the main argument people make for masking: that showing your real site's content makes the sending domain look like your company. In our checks, the filtering vendor judged sending domains by how they sent, not by the page they led to.
What we recommend
- A clean permanent redirect. A standard 301 over HTTPS, on both the bare domain and
www. Keep the path and query string, sogetacme.com/pricing?ref=emaillands onacme.com/pricing?ref=email. Search engines get an unambiguous signal about which domain is the original. - A hosting address that isn't a cluster of outreach domains. Whatever serves the redirect, avoid a single address shared by large numbers of sending domains. If listings start to cluster on one address, the address is the problem, not your page.
- A real, live destination. Point the redirect at a working page on your main site. A redirect to a dead page is no better than no redirect.
- No parked or empty pages. A domain that loads nothing, or a registrar's parking page, looks unfinished to the prospects who check it.
Winnr sets up 301 redirects, not masking. Set a redirect on the Domains page, or in the purchase wizard when you buy domains. For domains whose DNS Winnr manages, Winnr publishes the records, serves the redirect over HTTPS on the bare domain and www, and keeps the path and query string. If you connected a domain with manual DNS records, the Domains page shows the one A record to publish. See Domain redirects and email forwarding for the steps.
When masking still makes sense
Masking is a reasonable choice when you specifically want visitors to stay on the sending domain, for example a separate brand that should not show your main domain, and your site allows itself to be framed. If that's the goal, a simple one-page site hosted on the sending domain is often more robust than masking: it has its own content, works with any security headers, and doesn't depend on framing.
Whichever you pick, the hosting address matters more than the method. Blocklists and mailbox providers keep refining how they connect domains, so we keep measuring listing signals across the domains on our platform and will update this recommendation if the data points somewhere new.
The bigger deliverability picture
A well set-up redirect keeps your domain from inheriting problems it didn't cause. The factors that most decide whether a domain stays clean are still:
- The domain itself. Established TLDs are listed far less often than cheap, high-abuse ones. See how TLD choice affects deliverability.
- How it sends. Volume per mailbox, ramp-up and consistency.
- Who it sends to. List quality, spam traps and complaint rates.
If you are buying new sending domains, cold email domains bought through Winnr can have the redirect and a forwarding address set in the purchase wizard, so they never sit parked.
Related guides: Cold email DNS setup checklist, why Winnr uses DMARC p=reject, how to recover a burned domain, and the best cold email infrastructure providers.
Frequently Asked Questions
Is domain masking good for cold email?
It works, but it is rarely the best choice for a sending domain. A clean 301 redirect to your main site is simpler, does not break when your site blocks framing, and tells search engines which domain is the original. Our research found that what affects blocklist grouping is the web address a domain resolves to, and masking does not change that on its own.
What's the difference between a redirect and domain masking?
A redirect sends the visitor on to your main website, so the address bar changes to your main domain. Domain masking shows your site's content while the address bar stays on the sending domain, usually by loading the site inside a full-page frame or by re-serving it through a proxy.
Does a sending domain's redirect affect deliverability?
It can. For one major URI blocklist, domains that shared a web address with already-listed domains were listed noticeably more often in our data. Other major domain blocklists did not show that pattern. Avoid addresses that are crowded with outreach domains, whichever method you use.
Should my sending domain redirect to my main website?
In most cases, yes. A domain that loads nothing or shows a parked page looks unfinished to prospects who check it. A permanent redirect shows the domain belongs to a real company and tells search engines which domain is the original.
Does Winnr offer domain masking?
No. Winnr sets up 301 redirects. Set a redirect on the Domains page or in the purchase wizard and Winnr publishes the DNS records, serves the redirect over HTTPS on the bare domain and www, and keeps the path and query string. If you connected a domain with manual DNS records, the Domains page shows the A record to publish.
Does the redirect keep the page and tracking parameters?
Yes. The path and query string carry over, so a link to a specific page with tracking parameters on your sending domain lands on the same page, with the same parameters, on your main site.