Is 'AD' still required in subject lines for emails sent in China?
Michael Ko
Co-founder & CEO, Suped
Published 17 Jun 2025
Updated 18 Aug 2025
7 min read
When engaging with the Chinese market through email, marketers often encounter unique challenges and specific regulatory requirements. Unlike many other regions, China has distinct rules governing commercial email. A common question that arises is whether the inclusion of "AD" in the subject line is still a mandatory practice for emails sent within or into China.
I frequently hear concerns about how to navigate these rules effectively to ensure messages reach their intended recipients without being blocked or diverted to spam folders. Understanding these nuances is crucial for successful email campaigns in this significant market.
The "AD" requirement: Is it still valid?
Yes, the "AD" prefix in the subject line for commercial emails remains a requirement under Chinese anti-spam legislation. This is consistently noted across various sources, indicating its continued importance for email deliverability within China. For instance, Salesforce help documentation explicitly states that commercial emails must be labeled with "AD" or its Chinese equivalent. This requirement applies to promotional messages to help identify their nature.
While the regulation is clear, its effectiveness in preventing spam has been a subject of debate among deliverability professionals. Some argue that spammers simply comply, rendering the tag less useful for legitimate filtering. Despite these discussions, the legal obligation to include "AD" (or its Chinese character equivalent) for promotional emails persists. It's a compliance measure that, if overlooked, can lead to your emails being heavily filtered or even blacklisted (or blocklisted) by major Chinese Internet Service Providers (ISPs).
Ignoring this specific requirement can result in significant deliverability issues, pushing your emails into junk folders or leading to outright rejection. This is not just a suggestion, but a regulatory mandate intended to inform recipients and aid ISPs in identifying commercial content. Therefore, for any marketing or promotional email destined for Chinese inboxes, including "AD" is a critical step for compliance and better inbox placement.
Regulatory landscape and practical implications
The underlying reason for the "AD" requirement stems from China's "Regulations on Internet Email Services" and other anti-spam measures. These regulations aim to combat unsolicited commercial email (spam) by making it easy for both users and ISPs to identify promotional content. By requiring the "AD" tag, the authorities intended to create a clear signal, theoretically allowing users to set up rules to filter such emails and enabling ISPs to apply specific processing.
However, the practical application often differs from the theoretical intent. While intended to help, some view the "AD" tag as largely ineffective against malicious spam, as spammers can easily comply with the superficial requirement. Despite this perceived ineffectiveness, complying with this rule is non-negotiable for legitimate senders. Failing to do so can trigger spam filters, increase bounce rates, and negatively impact your sender reputation, making it harder for all your emails to reach Chinese recipients.
Law's intent
Identification: Provide clear labeling for commercial emails.
Filtering: Enable ISPs and users to easily filter promotional content.
Compliance: Ensure senders adhere to anti-spam regulations.
Actual impact on deliverability
Effectiveness: Limited in stopping determined spammers, who can simply add the tag.
Risk: Non-compliance by legitimate senders leads to blocking or spam folder placement.
Perception: Can contribute to negative user perception if too many legitimate emails are tagged.
The Microsoft Dynamics 365 documentation also highlights the need to label promotional messages as "AD" in the subject line. This emphasizes that even major platforms sending into China acknowledge and advise adherence to this specific rule. Understanding the full scope of specific rules and guidelines to deliver emails to the Chinese market is essential for sustained success.
Beyond the subject line: comprehensive deliverability to China
While the "AD" tag is a foundational requirement, successful email deliverability in China involves a much broader strategy. Chinese ISPs like QQ.com, Sina.com, and others have stringent filtering mechanisms that go beyond just subject lines. These include content filtering for sensitive keywords, aggressive rate limiting, and a strong preference for local infrastructure and relationships. It’s not just about what you say, but how and from where you send it.
For example, best practices for email deliverability to QQ.com often involve dedicated sending IPs and domains, careful content localization, and adhering to strict volume limits. Similarly, improving email deliverability to Sina.com and Sina.cn requires an understanding of their specific rate limits and content policies. Issues like invalid characters in email subject lines can also arise, complicating delivery further. This integrated approach is vital to avoid blacklisting (or blocklisting) and ensure consistent inbox placement.
Factor
Impact on Deliverability
Action for Senders
Content filtering
Sensitive keywords (political/religious) can lead to blocks.
Avoid sensitive content, localize messages.
Rate limiting
ISPs impose strict limits on sending volume.
Warm up IPs slowly, distribute sending volume.
Infrastructure
Preference for local IPs and domains.
Consider dedicated IPs/domains for China traffic.
Sender reputation
High complaints or blacklisting impacts delivery.
Maintain clean lists, monitor feedback loops.
I've learned that a comprehensive strategy for Chinese email deliverability also involves maintaining a pristine sender reputation, warming up new IPs slowly, and actively monitoring engagement metrics. Authentication protocols like SPF, DKIM, and DMARC are also crucial, though sometimes implemented differently by Chinese ISPs compared to Western counterparts. A simple guide to DMARC, SPF, and DKIM can help ensure your basic email security is in place for all regions.
Best practices for email campaigns in China
To maximize your chances of inbox placement in China, focus on these key areas. First, always include "AD" (or its Chinese equivalent) at the beginning of your promotional email subject lines. This is a mandatory compliance step. Second, ensure your content is culturally relevant and free of sensitive political or religious topics, which are heavily censored. Keep subject lines concise, ideally under 35 characters, as advised by Microsoft for optimal display across various platforms.
Consider setting up separate sending domains and IP addresses specifically for your Chinese email traffic. This isolates your Chinese sender reputation from your global sending activities, which can be critical given the unique filtering rules. High complaint rates or blacklisting on Chinese ISPs can severely impact your ability to reach this audience. Regularly monitor your deliverability and adjust your sending practices based on performance data.
Example of a compliant subject line
[AD] Your Exclusive Offer for Chinese Customers!
This subject line example provides the required "AD" prefix while also being concise and enticing. Remember to also maintain strict opt-in practices and make unsubscribing clear and easy, as these factors also influence how ISPs perceive your sending practices. Addressing topics like what words and practices should be avoided in email subject lines can further enhance your content strategy.
Views from the trenches
Best practices
Always include "AD" or its Chinese equivalent in subject lines for commercial emails.
Segment your email lists and sending infrastructure specifically for China.
Adhere to cultural sensitivities and avoid politically charged content in your emails.
Common pitfalls
Ignoring the "AD" requirement, leading to high spam filtering and low deliverability.
Sending high volumes of email without proper IP warm-up for Chinese ISPs.
Failing to localize email content, which can trigger content filters.
Expert tips
Monitor your sender reputation meticulously with Chinese ISPs.
Keep subject lines short (under 35 characters) for better readability.
Ensure a clear and easy unsubscribe process for all recipients.
Marketer view
Marketer from Email Geeks says that the "AD" prefix is still required in subject lines for emails sent in China.
2020-06-11 - Email Geeks
Marketer view
Marketer from Email Geeks says the law's initial intention was to stop spam by mandating the "AD" tag, which proved largely ineffective for its intended purpose.
2020-06-11 - Email Geeks
Conclusion
Navigating email deliverability in China presents a distinct set of challenges, and the requirement to include "AD" in promotional email subject lines remains a fundamental aspect of compliance. While the effectiveness of this specific rule in combating spam is debated, its legal mandate means that ignoring it can lead to severe deliverability issues.
Beyond this specific subject line tag, successful email campaigns in China demand a holistic approach, including adherence to local content sensitivities, strategic IP and domain management, and a deep understanding of Chinese ISP behaviors. By combining regulatory compliance with robust technical and content best practices, you can significantly improve your chances of reaching the inbox in this complex, yet rewarding, market.
