Why are emails bouncing from Telia and iCloud with a 4.3.2 error?
Matthew Whittaker
Co-founder & CTO, Suped
Published 15 Jun 2025
Updated 18 Aug 2025
7 min read
Encountering email bounces can be frustrating, especially when they stem from major providers like iCloud and Telia with a specific 4.3.2 error code. This error, often indicating that the recipient's system is not accepting network messages, can initially seem like a temporary glitch. However, if persistent, it signals deeper issues with your sending practices or sender reputation.
When you're migrating to a new email sending system, like from Campaign Monitor to Salesforce, these types of bounce errors are particularly concerning. A sudden shift in sending infrastructure can trigger aggressive spam filters, leading to significant delivery failures. Understanding the nuances of the 4.3.2 error and how it relates to providers like Telia and iCloud is crucial for restoring your email deliverability.
Understanding the 4.3.2 error
A 4.3.2 error is generally classified as a soft bounce, implying a temporary issue rather than a permanent rejection. The common message associated with it, “system not accepting network messages,” suggests that the recipient's mail server is temporarily unavailable or overloaded. However, it can also be a blanket error for other temporary problems, such as rate limiting or even a form of greylisting.
While soft bounces are expected to resolve themselves after a retry period, repeated 4.3.2 errors, especially for a large volume of recipients, can indicate that your sending IP or domain has a reputation problem. Mailbox providers, including Telia and iCloud, use these temporary rejections to evaluate sender behavior before potentially applying harder blocks or even blacklisting (blocklisting) your sender. For more information, SenderScore has a detailed guide.
A key factor often overlooked is the sheer volume of emails being sent. Mailbox providers like Telia and iCloud are highly sensitive to sudden increases in sending volume from a new or unfamiliar IP address or domain. Even legitimate marketing or transactional emails can be flagged if they arrive in a burst that exceeds the recipient server's predefined thresholds. This is especially true during a migration, where a large volume of traffic might switch from an established sending system to a new one, causing it to look suspicious.
Understanding the 4.3.2 error
Nature: A soft bounce, implying a temporary issue on the recipient's server.
Meaning:4.3.2 system not accepting network messages or system full. Can also imply rate limiting.
Impact: Persistent 4.3.2 errors can be a sign of deeper reputation issues or aggressive filtering.
Why Telia and iCloud are particularly sensitive
Both Telia, a prominent Scandinavian telecommunications provider, and Apple's iCloud service (including me.com and mac.com), are known for their stringent spam filtering policies. They prioritize user experience, which means even minor red flags can lead to messages being rejected or sent to spam. This is particularly relevant when observing high bounce rates from iCloud.
For Telia, their filters often react to sudden volume changes from new or un-warmed IPs. If you've just switched to Salesforce, the new sending IPs are essentially unknown to Telia, making them cautious. This can result in a significant number of 4.3.2 errors as a protective measure against potential spam. Their systems are designed to detect abnormal sending patterns immediately.
iCloud (and other Apple email domains) are particularly sensitive to sender reputation and subscriber engagement. They prioritize emails that users actively interact with. If your migration involves sending to older, less engaged lists, or if the initial volumes are too high, iCloud might interpret this as suspicious activity. High volume of soft bounces from Apple addresses is a common sign of this, as noted by Salesforce.
Diagnosing the problem
When facing these bounce issues, the first step is to methodically diagnose the root cause. This involves checking various aspects of your email sending infrastructure and practices.
Migration challenges
Reputation Reset: New IPs or sending domains start with no reputation, triggering cautious ISP filters.
Volume Spikes: Migrating existing large lists to a new platform can cause sudden, high volume sending that is often flagged.
Start by checking the full bounce messages. While a 4.3.2 error is generic, the extended message (after the DSN, Delivery Status Notification) can provide more specific clues about why the recipient system is not accepting network messages. It might include phrases related to rate limits, temporary unavailability, or even reputation concerns.
Next, assess your sender reputation. If you've recently migrated to a new sending platform like Salesforce, the sending IP addresses and possibly your domain's reputation at Telia and iCloud are essentially starting from scratch. These providers may be greylisting or soft-bouncing your emails as a way to test your domain's sending behavior. Check if your IP or domain appears on any public blocklists (or blacklists). While Telia and iCloud primarily use internal reputation systems, some common blocklists can influence their filtering decisions. For a comprehensive overview, read our guide to email blocklists.
Solutions and best practices
The good news is that 4.3.2 errors are usually solvable with a strategic approach to your email sending. The key is to demonstrate consistent, positive sending behavior to build trust with Telia and iCloud.
Recommended actions
IP Warming: Gradually increase sending volume from your new Salesforce IPs. Start with your most engaged subscribers.
List Hygiene: Regularly clean your email lists to remove inactive subscribers, which can reduce bounces and improve engagement metrics.
Engagement Focus: Send highly relevant content to drive opens and clicks, signaling positive intent to ISPs. This can prevent your emails from going to spam.
For iCloud specifically, consistent high engagement is key. Ensure your subscriber list is healthy and that you're only sending to active, opted-in users. Any signs of low engagement or high complaints can trigger their filters. Consider segmenting your iCloud recipients and sending smaller batches initially, observing how they respond before scaling up. This proactive approach helps fix email delivery issues.
If your domain or IP address ends up on a public blacklist, prompt action is required. Review the listing reason, rectify any underlying issues (like sending to spam traps), and then request delisting. Continued monitoring of blocklists is essential for long-term deliverability. Remember, building a good sender reputation takes time and consistent effort, particularly with providers known for strict filtering.
It’s important to remember that email deliverability is an ongoing process. Implementing these solutions and continuously monitoring your performance will help you maintain a strong sender reputation and ensure your emails reach Telia and iCloud inboxes. Regular deliverability testing and monitoring is key, and a proven checklist for email deliverability tests can be invaluable.
Views from the trenches
Best practices
Always warm up new sending IPs gradually, especially when migrating to a new platform like Salesforce, to build trust with ISPs.
Segment your email lists and prioritize sending to your most engaged subscribers first when introducing a new sending infrastructure.
Implement and verify SPF, DKIM, and DMARC records correctly for your new email setup to ensure strong email authentication.
Regularly monitor your domain and IP reputation using tools and feedback loops provided by mailbox providers.
Proactively clean your email lists by removing inactive or bouncing addresses to maintain good sender hygiene and improve engagement metrics.
Ensure your email content is relevant and provides value to encourage positive subscriber engagement like opens and clicks.
Common pitfalls
Migrating an entire email list to a new sending system all at once, leading to sudden volume spikes that trigger spam filters.
Neglecting to warm up new sending IPs, resulting in immediate blocks or high bounce rates from sensitive ISPs like Telia and iCloud.
Failing to properly configure email authentication protocols (SPF, DKIM, DMARC) on the new platform, causing messages to fail validation.
Sending to old, unengaged email lists after a migration, which can lead to high bounce rates and spam complaints, damaging reputation.
Not monitoring bounce messages closely for specific error codes beyond the generic ones, missing critical diagnostic information.
Ignoring public or private blocklist listings, which can prevent emails from reaching their intended recipients until resolved.
Expert tips
A sudden shift in sending infrastructure often triggers more aggressive spam filters, so plan your migration carefully.
Even legitimate emails can be flagged if they arrive in a burst exceeding recipient server thresholds, especially from new IPs.
I often see 4.3.2 errors used as a blanket error for various temporary problems, including rate limiting.
Telia and iCloud are known for stringent spam filtering policies and prioritize user experience, so slight red flags lead to rejections.
iCloud is sensitive to sender reputation and subscriber engagement; low interaction signals suspicious activity.
The full bounce message, beyond the initial 4.3.2, can provide more specific clues for diagnosis.
Marketer view
Marketer from Email Geeks says they were seeing emails not getting through to Telia recipients and that it was hard to determine why without seeing the bounce messages.
2019-05-08 - Email Geeks
Marketer view
Marketer from Email Geeks says they saw a single open out of several thousand for emails sent through a new system, compared to hundreds of opens with the old system.
2019-05-08 - Email Geeks
Ensuring smooth email delivery
The 4.3.2 bounce error from Telia and iCloud, particularly during a migration, signals that these providers are scrutinizing your sending patterns. It's a call to action to review your email practices, ensure proper authentication, and manage your sending volume carefully. By understanding their strict filtering policies and proactively addressing potential issues, you can significantly improve your email deliverability.
Focus on building a strong, positive sender reputation by sending relevant emails to engaged subscribers and adhering to best practices. Continuous monitoring and quick responses to bounce patterns will help maintain healthy email flows, ensuring your messages consistently reach their intended recipients at Telia, iCloud, and beyond. For broader insights into email deliverability challenges, consider reading our article on email deliverability issues.
iCloud and Telia with a specific 4.3.2 error code. This error, often indicating that the recipient's system is not accepting network messages, can initially seem like a temporary glitch. However, if persistent, it signals deeper issues with your sending practices or sender reputation.
Telia, a prominent Scandinavian telecommunications provider, and 
Apple's iCloud service (including me.com and mac.com), are known for their stringent spam filtering policies. They prioritize user experience, which means even minor red flags can lead to messages being rejected or sent to spam. This is particularly relevant when observing high bounce rates from iCloud.
