How does domain blocking in some countries affect email deliverability and image rendering?
Michael Ko
Co-founder & CEO, Suped
Published 25 Jun 2025
Updated 18 Aug 2025
7 min read
When managing email campaigns, a common concern arises: how does domain blocking in specific countries affect overall email deliverability and the rendering of images within those emails? It's a complex issue, as digital boundaries and censorship measures vary significantly from one nation to another.
The immediate thought might be that if a website or domain is blocked in a country, all associated email communications would also cease to function. While there's a degree of truth to this, the impact isn't always as straightforward as a complete global blackout. Typically, country-specific blocking is localized.
Understanding the nuances of how these blocks are implemented, whether at the DNS level or content filtering, is key to assessing their effect on your email program. We will explore the mechanisms behind domain blocking and its specific implications for your email deliverability and image display in emails.
Understanding country-level domain blocking
Country-level domain blocking often stems from government regulations or internet service provider (ISP) policies. These measures typically target website access rather than direct email transmission protocols. The blocking usually occurs at the DNS (Domain Name System) level, where attempts to resolve a blocked domain name within that country are simply redirected or fail to resolve.
For instance, if a domain like example.com is blocked in Vietnam, users in Vietnam attempting to access the website would find it unreachable. This type of block is primarily about content access and does not inherently mean that emails sent from promo@example.com will also be blocked globally or even within Vietnam, unless other factors are at play.
It's crucial to differentiate between a website block and an email deliverability block (or blacklist). While related, they operate on different principles. A website block prevents browsing, whereas email blocklists (or blacklists) prevent mail from reaching the inbox, often due to sender reputation issues or spam complaints. To learn more about email blocklists, you can consult an in-depth guide to email blocklists.
Impact on email deliverability
The primary impact of country-level domain blocking on email deliverability is localized. If a domain is blocked at the DNS level within a specific country, email authentication mechanisms such as SPF, DKIM, and DMARC might fail for recipients in that country. This is because these protocols often rely on DNS lookups to verify the sending domain. If the DNS lookup for your domain fails, the recipient's mail server may not be able to authenticate your email properly, leading to delivery issues within that country.
However, this typically does not impact global email deliverability, provided your sending reputation is strong elsewhere. Mailbox providers and ISPs outside the blocked region will perform their own DNS lookups, which would be unaffected by country-specific blocks. The exception would be if a major global email service provider (ISP), such as Google, has infrastructure or servers within the blocked country that are forced to comply with local blocking regulations.
A more direct and noticeable consequence of domain blocking can be on the rendering of images within your emails. Most email images are not embedded directly into the email itself; instead, they are hosted on a web server and linked within the HTML of the email. When a recipient opens an email, their email client fetches these images from the hosted domain.
If the domain where your email images are hosted is blocked in a specific country, recipients in that country will likely not see the images. This is because their email client's attempt to access the image hosting domain will be blocked, preventing the images from loading. This can severely degrade the user experience and the effectiveness of image-heavy email campaigns.
Minimal direct impact on email delivery to unblocked regions.
Images hosted on blocked domain will not render.
Country-specific.
DNS-level Blocking
Significant impact on deliverability to blocked regions due to authentication failures (SPF, DKIM, DMARC).
Images hosted on blocked domain will not render, due to failed DNS resolution.
Country-specific, potentially affecting global services located within.
Email Blocklists (Blacklists)
High impact globally if domain or IP is listed, leading to messages being filtered to spam or rejected.
Images may or may not render depending on mail client, but primary issue is email delivery.
Global or regional, depending on the blocklist.
Mitigating risks and maintaining deliverability
To mitigate the risks associated with country-level domain blocking and ensure optimal email deliverability, several proactive steps can be taken. The first involves understanding your email infrastructure and how it interacts with different regional networks. While you can't control government blocking, you can control your sending practices.
Maintaining a strong sender reputation is paramount. ISPs widely use sender reputation as a key criterion to decide whether to deliver emails to the inbox or filter them into the spam folder. A poor reputation can lead to emails being blocked or filtered, even if the blocking is not directly related to country-specific restrictions. For comprehensive strategies, explore guides on email deliverability and sender reputation.
Regularly monitoring your domain and IP for blocklist (or blacklist) listings is essential. Getting listed on a blocklist can severely impact your deliverability across multiple regions, not just those with country-specific blocks. Tools and services can help you stay on top of your reputation and address any issues promptly. This can be especially important for issues like CBL domain listings.
Finally, for image rendering, consider hosting images on a Content Delivery Network (CDN) with points of presence (PoPs) in various regions, or potentially using a different domain for image hosting that is less likely to be blocked. However, be mindful of how the hostname used for image hosting affects deliverability or custom domains for image hosting impact reputation. Adhering to sender guidelines, such as those provided by Google, is also a foundational step.
Views from the trenches
Best practices
Maintain a robust sender reputation globally by ensuring consistent engagement and avoiding spam complaints.
Always include descriptive alt text for all images in your emails to ensure readability even if images are blocked.
Implement and monitor email authentication protocols like SPF, DKIM, and DMARC for all sending domains.
Common pitfalls
Assuming country-level website blocking automatically means global email deliverability failure, which is not always the case.
Neglecting email content design in scenarios where images might not render, leading to a poor user experience.
Overlooking DNS-level blocking effects on email authentication, causing delivery failures in specific regions.
Expert tips
Regularly test your email deliverability to various global regions to identify potential issues early.
Diversify your image hosting strategy if you frequently encounter rendering issues in specific geographic areas.
Keep abreast of internet censorship laws and policies in key target markets to anticipate potential blocking issues.
Marketer view
Marketer from Email Geeks says that website blocking at a country level is typically specific to those countries and should not affect global email deliverability, provided the domain's sending reputation remains strong elsewhere. Email sending to blocked countries would also likely fail.
2022-12-14 - Email Geeks
Marketer view
Marketer from Email Geeks notes that domain blocking can affect deliverability to specific countries if it occurs at the DNS level, preventing authentication lookups and MX record verification. This can cause emails to fail delivery.
2022-12-14 - Email Geeks
Ensuring global email reach
While country-level domain blocking primarily impacts website accessibility, its effect on email deliverability is generally limited to the specific blocked regions, especially if DNS-level blocking prevents authentication checks. Global email deliverability remains largely unaffected, provided your domain maintains a strong sender reputation and proper authentication.
The more significant direct impact is on image rendering within emails, as images hosted on blocked domains will fail to load. By focusing on robust email authentication, maintaining a stellar sender reputation, and designing emails that are effective even without images, you can significantly mitigate the risks posed by such regional restrictions.
Proactive monitoring and adherence to email best practices are always your strongest defenses in ensuring your messages reach their intended audience, regardless of geopolitical digital barriers.
Google, has infrastructure or servers within the blocked country that are forced to comply with local blocking regulations.
