Why are there soft bounces at Yahoo and AOL for opted-in weekly newsletters?
Matthew Whittaker
Co-founder & CTO, Suped
Published 2 Jun 2025
Updated 18 Aug 2025
8 min read
It can be incredibly frustrating to see a high volume of soft bounces, especially when sending opted-in weekly newsletters to subscribers on major mailbox providers like Yahoo and AOL. The situation can feel particularly perplexing when emails deliver successfully one week, only to soft bounce the next, creating an inconsistent and concerning pattern.
This intermittent bouncing, often characterized by 421 errors or TS04 bounce codes, suggests that while the recipient address is valid, delivery is being temporarily delayed or blocked by the recipient's server. It is a common challenge for senders, even those with strong sender reputations and highly engaged lists.
Understanding why these soft bounces occur, particularly with Yahoo and AOL (now part of Verizon Media Group), is crucial for maintaining consistent email deliverability for your newsletters. Let us explore the factors contributing to these issues and how to address them effectively.
Understanding soft bounces
A soft bounce indicates a temporary email delivery failure. Unlike a hard bounce, which means the email address is permanently invalid, a soft bounce suggests that the email server could not deliver the message at that specific moment, but it might be able to do so later. Common reasons for a soft bounce include a full inbox, a temporary server issue, or the recipient's server throttling incoming mail due to volume or perceived reputation issues.
For Yahoo and AOL, soft bounces often stem from their aggressive filtering systems and strict reputation management. Even for opted-in lists, these providers may temporarily defer (soft bounce) emails if they detect unusual sending patterns, high volume spikes, or if your sending IP or domain reputation is not perfectly aligned with their expectations. This is particularly true for weekly newsletters, which involve recurring, predictable sends that these systems are constantly evaluating.
What is a soft bounce?
A soft bounce signifies that an email could not be delivered on the first attempt but is not a permanent failure. The email service provider (ESP) will typically retry sending the email for a period, after which it might convert into a hard bounce if delivery remains unsuccessful. Understanding these temporary failures is key to troubleshooting and resolving soft bounces effectively. You can learn more about general soft bounce reasons from Mailgun's explanation.
The pattern of weekly bounces followed by periods of successful delivery points to dynamic filtering by Yahoo and AOL (now part of Yahoo's larger entity, AOL). These providers use sophisticated algorithms to protect their users from unwanted mail, which can sometimes result in legitimate mail being deferred. When they perceive a slight increase in volume or a minor dip in engagement for a particular sender, they might temporarily throttle or block messages to assess the sending behavior further. This often manifests as 421 errors or TS04 bounces, indicating a temporary system error or a volume-based filter at the recipient's end.
Common causes at Yahoo and AOL
One primary reason for these specific soft bounces is the reputation of your sending IP and domain. Even if your list is opted-in, Yahoo and AOL are highly sensitive to sender reputation. If your IP address and domain are not consistently warmed up or if they have had recent fluctuations in email volume, engagement, or complaint rates, these providers might temporarily delay your emails. They prefer to receive mail from senders with a known and consistent positive sending history.
Another factor is Yahoo and AOL's aggressive throttling policies. They may limit the number of emails accepted from a particular IP address or domain within a specific timeframe. When you send a large weekly newsletter, a sudden surge in volume could trigger these filters, leading to 421 errors. This is a common defense mechanism against spam and can affect even legitimate senders. Salesforce notes that these errors often result from volume-based filters at the recipient's end.
Temporary filtering issues
Soft bounces like 421 errors or TS04 can indicate temporary server overloads, a full recipient inbox, or immediate throttling due to high sending volume to a specific domain. These are usually not indicative of a permanent block but signal that the recipient's server is temporarily unavailable or overwhelmed. You may face soft bounce issues with Yahoo/VZG email even with legitimate emails.
Moreover, Yahoo and AOL have recently implemented stricter sender requirements aimed at reducing spam. These changes, affecting both Gmail and Yahoo email clients, emphasize authenticated sending via SPF, DKIM, and DMARC, as well as maintaining low spam complaint rates. If your email authentication isn't perfectly configured or if your complaint rates creep up, even slightly, it can trigger temporary blocks or soft bounces for your newsletters. For a general guide on why AOL and Yahoo emails bounce, see our detailed article.
Resolving the issues
The first step to resolving persistent soft bounces is to identify the specific bounce codes provided by your email service provider (ESP). While many might simply show 'SoftBounceGeneral,' digging into your ESP's logs for detailed bounce messages can reveal the underlying cause, such as 421 errors or TS04 bounces, which indicate temporary issues often related to reputation or volume.
If the problem is recurring, especially with opted-in weekly newsletters, you should proactively engage with Yahoo and AOL's sender support portals. Submitting a ticket with your sending IP, domain, and specific examples of the soft bounces (including the full bounce message) can help them investigate and potentially whitelist your sending infrastructure or provide specific guidance. This is particularly effective for TS04 delays, which are often tied to how well-known your IP and sending history are to them.
Beyond direct communication, consistent email authentication (SPF, DKIM, DMARC) is non-negotiable. Ensure your DNS records are correctly configured and validated. These protocols prove to recipient servers that your emails are legitimate and authorized, significantly improving your sender reputation. If your email authentication is not correctly set up, your emails may be flagged as suspicious and result in soft bounces or even being added to a blocklist (or blacklist). For more on this, check out our simple guide to DMARC, SPF, and DKIM.
Maintaining good deliverability
Maintaining an excellent sender reputation is paramount. This means consistently sending wanted mail, keeping complaint rates extremely low, and ensuring high engagement. Even with opted-in lists, inactive subscribers can negatively impact your reputation. Regularly cleaning your list of unengaged or inactive subscribers helps signal to mailbox providers that you are a responsible sender.
Monitor engagement closely: Pay attention to open and click rates specifically for Yahoo and AOL recipients. Low engagement can lead to higher filtering.
Segment inactive users: Consider segmenting or suppressing subscribers who have not engaged with your newsletters for a significant period. This reduces the risk of hitting spam traps or being marked as spam.
Warm up new IPs/domains gradually: If you change sending infrastructure, a careful warm-up process is essential to build trust with providers like Yahoo and AOL.
Keep content relevant: Even for opted-in lists, irrelevant content can lead to complaints, which are highly detrimental to sender reputation.
For ongoing issues with Yahoo and AOL email engagement and delivery rates, it is crucial to remain vigilant. Regularly check your sending metrics and respond quickly to any spikes in soft bounces. By proactively managing your sender reputation and adhering to best practices, you can significantly reduce the occurrence of soft bounces and ensure your valuable newsletters reach their intended recipients reliably.
Focus on sender reputation
Yahoo and AOL prioritize sender reputation above all. A strong reputation, built on consistent sending practices and low complaint rates, is vital for reliable delivery. This includes carefully managing your sending domain reputation. Consider our article on technical solutions from top performing senders.
Address volume spikes
Sudden increases in sending volume, even for opted-in lists, can trigger throttling. Yahoo and AOL may interpret this as suspicious activity. Maintaining a consistent sending volume and gradually increasing it over time helps build a predictable sending pattern that these providers trust.
Views from the trenches
Best practices
Always include clear unsubscribe links that work instantly for opted-in newsletters.
Segment your audience based on engagement and send less frequently to less engaged subscribers.
Routinely clean your mailing list to remove inactive or bouncing addresses.
Common pitfalls
Ignoring bounce messages and not analyzing the specific codes for patterns.
Sending to inactive subscribers who haven't opened emails in over 6-12 months.
Not warming up new sending IPs or domains gradually before sending large volumes.
Expert tips
Regularly check your DMARC reports for insights into authentication failures and potential issues.
Utilize Yahoo's Sender Portal to proactively engage with their deliverability team if you see consistent issues.
Implement a double opt-in process for all new subscribers to ensure high quality and engagement.
Marketer view
A marketer from Email Geeks says that encountering
2022-06-21 - Email Geeks
Expert view
Expert from Email Geeks says that the specific bounce message is crucial for troubleshooting, as Yahoo provides data and links to help with problem resolution.
2022-06-21 - Email Geeks
Navigating intermittent soft bounces
The intermittent soft bounces you observe at Yahoo and AOL for opted-in weekly newsletters are a known challenge in the email deliverability landscape. They often stem from a combination of temporary filtering, volume-based throttling, and the specific reputation signals these providers detect for your sending IP and domain. While frustrating, these issues are usually not permanent and can be managed with a proactive approach.
By understanding the root causes, meticulously monitoring your bounce codes, engaging with Yahoo and AOL's sender support, and rigorously adhering to email best practices (especially regarding authentication and list hygiene), you can significantly improve your newsletter's consistent inbox placement. Ongoing vigilance and optimization of your sending practices are key to ensuring your messages consistently reach your engaged audience.
