How to improve email deliverability to Sina.com and Sina.cn in China and handle rate limits?
Michael Ko
Co-founder & CEO, Suped
Published 1 Jul 2025
Updated 18 Aug 2025
7 min read
Email deliverability in China, especially to providers like Sina.com and Sina.cn, poses unique challenges compared to sending emails in Western markets. We often encounter issues like low acceptance rates and strict rate limits, typically indicated by errors such as 452 Too many recipients received this hour. This error signifies that the recipient server is temporarily rejecting emails because your sending IP has exceeded their hourly volume threshold.
The Chinese internet infrastructure and regulatory environment are distinctly different, impacting how emails are processed and delivered. Unlike many global ISPs, Chinese providers operate with a stronger focus on controlling information flow and managing network resources, which translates into stricter sending policies and content filtering. This guide explores strategies to navigate these complexities and improve your email deliverability to Sina.com and Sina.cn.
Understanding the unique landscape of Chinese email providers
Sending emails into China is not the same as sending them elsewhere. Chinese ISPs, including Sina.com and Sina.cn, have evolved their systems to prioritize transactional emails while often treating bulk or marketing emails with higher scrutiny. This is partly due to the prevalence of local messaging apps like WeChat, QQ, and DingTalk for marketing and general communication, leading to a different expectation for email usage.
A critical aspect is content filtering. Email content is subject to strict review for political, religious, or other sensitive topics, which can lead to blocks or blacklists. To avoid content filtering, ensure your emails are primarily in Chinese and adhere to local cultural norms. English-only content or content that might be deemed sensitive is often flagged, resulting in delivery failures. For more detailed insights into email content guidelines in China, external resources offer valuable advice.
Another factor is the origin of your sending IP addresses. Some experience suggests that sending from Chinese IP ranges (APNIC) may result in better performance. If you are using a global email service provider, confirm whether they have infrastructure or partnerships within China that utilize local IP addresses, as this can significantly improve deliverability rates to Sina.com and Sina.cn.
Strategies for managing rate limits
The rate limit error 452 Too many recipients received this hour is a clear indicator that Sina.com and Sina.cn are actively throttling your sending volume. Their systems are designed to accept emails at a much slower pace than many Western ISPs, requiring senders to adapt. One common recommendation is to significantly reduce your sending rate. While precise figures can vary, some senders have found success by limiting their volume to as low as 8 messages per minute or around 500 emails per hour to Sina domains.
Common Sina.com Rate Limit Errorplaintext
452 Too many recipients received this hour. p=ca1-452 83.195.78.238
Implementing a dynamic throttling mechanism that adjusts based on recipient server responses is crucial. When you receive a 452 error, your system should automatically pause sending to that domain for a period and then retry at a reduced rate. Continuously hitting these limits without adjusting can negatively impact your sender reputation and lead to longer-term blocks (or blocklists).
For many businesses, this level of throttling can be challenging, especially for transactional emails that require immediate delivery. It highlights a fundamental difference in email infrastructure. While it's not ideal for high-volume marketing campaigns, adhering to these lower limits is necessary to maintain a positive sending relationship with Chinese ISPs. For more information on handling email sending rate and connection limits, we have detailed guides available.
Important rate limit advice
Sina.com and Sina.cn enforce some of the strictest rate limits among major ISPs. If you are experiencing 452 Too many recipients errors, drastically reduce your sending volume to these domains. Some senders have reported success with rates as low as 8 messages per minute or 500 emails per hour initially. Gradually increase only if deliverability improves consistently.
Building and maintaining a strong sender reputation
A strong sender reputation is paramount for deliverability to any ISP, and Sina is no exception. While they may have unique filtering, fundamental best practices still apply. This includes rigorous list hygiene, ensuring your contact lists are clean and free of invalid or inactive addresses. High bounce rates signal poor list quality and can quickly damage your sender score. Regularly removing unengaged subscribers is a key part of this process.
Chinese ISPs heavily rely on sender accuracy metrics, such as read rates and delete rates, to gauge your reputation. This means not only getting emails into the inbox but also ensuring recipients find them relevant and engaging. A low read rate or high delete rate can lead to your emails being marked as spam, even if you pass technical authentication. Focusing on valuable content and segmenting your audience carefully will help improve these metrics.
Consider using separate sending domains for transactional and marketing emails. This allows Chinese ISPs to differentiate between critical communications and promotional content, helping to maintain the reputation of your transactional domain even if marketing sends encounter issues. It's a strategic move to isolate potential problems and protect your most important email streams. Monitoring your IP and domain for blacklists (or blocklists) is also essential, as getting listed on a blocklist can severely impact deliverability.
Positive reputation practices
Engagement focused: Send emails that are highly relevant to recipients, leading to higher open and click-through rates and fewer complaints.
Content flags: Triggering filters with sensitive or off-topic content can lead to delivery failures.
Content and authentication considerations
Beyond rate limits and reputation, the technical setup of your email sending infrastructure plays a vital role. Proper email authentication, including SPF, DKIM, and DMARC, is non-negotiable for improving deliverability anywhere, and especially in China. These protocols verify that your emails are legitimate and prevent spoofing, which helps build trust with recipient servers. Without these, your emails are far more likely to be flagged as suspicious or spam.
For example, a robust DMARC policy at Sina.com, even in a relaxed p=none reporting mode, provides valuable feedback through DMARC reports. These reports can show you authentication failures, helping you identify and fix issues that might be hindering your deliverability.
The table below outlines the core authentication methods and their role in ensuring your emails are trusted by Sina and other Chinese ISPs:
Authentication type
Description
Impact on Sina deliverability
SPF
Sender Policy Framework, a DNS record specifying authorized sending servers.
Helps prevent spoofing by allowing Sina to verify sender identity.
DKIM
DomainKeys Identified Mail, a digital signature that verifies email integrity and sender identity.
Critical for establishing trust; ensures messages haven't been tampered with.
DMARC
Domain-based Message Authentication, Reporting & Conformance, builds on SPF and DKIM.
Provides policy control and reporting, crucial for understanding deliverability issues to Sina.
Beyond authentication, avoid URL shorteners and excessive links, which can raise spam flags. Also, keep your email campaigns segmented and personalized to maximize engagement and minimize the chances of being marked as spam. For those also sending to QQ.com, a different set of considerations might apply due to their specific infrastructure and user base, although many fundamental deliverability practices remain the same.
Views from the trenches
Best practices
Maintain an extremely slow sending rate to Sina.com and Sina.cn, possibly below 500 emails per hour.
Prioritize sending emails in simplified Chinese language and avoid sensitive topics.
Implement strong SPF, DKIM, and DMARC records to authenticate your emails effectively.
Use separate sending domains or IPs for transactional and marketing emails to isolate deliverability issues.
Common pitfalls
Attempting to send at high volumes to Sina domains, which will lead to immediate rate limiting and rejections.
Sending emails primarily in English or with content that could be flagged by Chinese content filters.
Neglecting email authentication, making your emails appear untrustworthy to Chinese ISPs.
Using the same IP addresses for both high-volume marketing and critical transactional emails, risking both streams.
Expert tips
Chinese email infrastructure is optimized for transactional emails; rethink bulk marketing campaigns.
Consider engaging with a local provider or partner who has established relationships and local IP resources.
Monitor your deliverability metrics specifically for Chinese domains to understand what works and what doesn't.
An indirect contact with Sina's postmaster team can sometimes resolve persistent deliverability issues.
Marketer view
Marketer from Email Geeks says delivery to China can be challenging when sending from outside, suggesting that using Chinese or APNIC range IPs might improve performance. They also noted that whitelisting might be an option.
1744029810 - Email Geeks
Marketer view
Marketer from Email Geeks says Sina's usual recommendation for deferral messages is to stop sending from that IP and then reduce volume, suggesting throttling sends to below 500 emails per hour.
1744030618 - Email Geeks
Navigating the Chinese email landscape
Improving email deliverability to Sina.com and Sina.cn requires a multifaceted approach that acknowledges the unique characteristics of the Chinese email ecosystem. It is not a simple matter of increasing volume or applying standard global best practices; rather, it demands patience, careful monitoring, and a willingness to adapt to local rules and infrastructure.
By understanding the strict rate limits, prioritizing local language content, maintaining impeccable sender reputation, and ensuring robust email authentication, you can significantly enhance your chances of reaching the inbox. Remember, consistency and adherence to these guidelines are key to building a reliable email presence within China.
Sina.com, even in a relaxed p=none reporting mode, provides valuable feedback through DMARC reports. These reports can show you authentication failures, helping you identify and fix issues that might be hindering your deliverability.
Sina to verify sender identity.
