Summary
Emails bouncing when sent to T-Online subscribers via Klaviyo can be a frustrating experience, especially when other recipients are receiving your messages without issue. This specific problem often points to particular deliverability challenges associated with T-Online, a major German internet service provider. While Klaviyo manages much of the underlying infrastructure, the root cause can range from shared IP reputation issues to specific configuration requirements T-Online enforces. Understanding these nuances is crucial for restoring your email deliverability to T-Online addresses.
Key findings
- Common issue: Bounces to T-Online users are a widespread problem encountered by many senders, not just a niche occurrence, as many in the email community have reported.
- Shared IP challenges: If you are on a shared IP address (common with ESPs like Klaviyo), your deliverability can be impacted by the sending practices of other users on the same IP. This could lead to a shared IP being added to a blocklist or its reputation being damaged, even if your own sending practices are good.
- Specific ISP requirements: T-Online (and other ISPs like Arcor.de) can have unique and strict requirements regarding sender reputation, DNS configuration (such as SPF, DKIM, and DMARC records), and even the presence of contact information on your website.
- Dedicated IP nuances: Transitioning to a dedicated IP requires careful warming up, and excluding certain ISPs during this phase is generally not recommended as it hinders the reputation building process with those providers.
Key considerations
- Retrieve bounce messages: The most crucial step is to obtain the exact bounce messages from T-Online. These messages often contain specific error codes or descriptions that can pinpoint the exact reason for the rejection.
- Contact Klaviyo support: If on a shared IP, reach out to Klaviyo's technical support. They may be able to address a broader blocklist issue with T-Online or even move you to a different IP pool with a better reputation. You should also refer to their official documentation on T-Online.de inbox placement requirements.
- Review DNS configuration: Ensure your DNS records, including SPF, DKIM, and DMARC, are correctly configured for your sending domain. T-Online can be particular about these. You can learn more about this in our guide to DMARC, SPF, and DKIM.
- Website contact information: Verify that your website has clear and easily accessible contact information, as some ISPs, including T-Online, may check for this as a sign of legitimate sending.
- Warm up dedicated IPs correctly: If you are warming up a new dedicated IP, do not exclude T-Online subscribers. Instead, continue sending to them, monitor bounces, and use bounce data to inform your engagement with T-Online's postmaster if necessary. This will help build a proper sending reputation with all ISPs, including T-Online.
- Monitor your sender reputation: Keep a close eye on your sender reputation, as a degraded reputation can lead to blocklisting. Learn about what happens when your IP gets blocklisted.
What email marketers say
Email marketers often face a range of deliverability challenges, and T-Online bounces are a recurring theme. Their experiences highlight common points of frustration, from generic bounce messages to the complexities of managing shared IP reputations within an ESP environment. Marketers emphasize the importance of understanding the specific nature of bounces and the impact of provider-level issues on their campaigns, even when their own sending practices are sound.
Key opinions
- Generic bounces: Many marketers find that the bounce messages from T-Online are uninformative, making it difficult to diagnose the exact issue without further investigation.
- Widespread problem: There's a general consensus among marketers that encountering bounces at T-Online is a common occurrence, suggesting it's not isolated to a single sender.
- ESP-level issues: When sending via a platform like Klaviyo, marketers often consider that shared IP blocklists or poor reputation from other users on the platform might be the cause of their deliverability woes.
- Impact on all products: Bounce issues with T-Online can affect all email types, including transactional emails, even if other emails generally experience good inbox placement.
Key considerations
- Engage ESP support: Marketers should actively engage their ESP's support team to investigate shared IP issues or request a move to a different IP pool if problems persist. Klaviyo advises on how to decrease bounce rates in general.
- Dedicated IP transition: When moving to a dedicated IP, marketers should understand that a proper warmup strategy is essential for establishing sender reputation with all ISPs, including T-Online. Excluding segments can hinder this process.
- List hygiene: Maintaining a clean email list is critical. Regularly remove inactive or unengaged subscribers to prevent bounces and preserve sender reputation, as highlighted in guides on Klaviyo list cleaning.
- Bounce analysis: Despite potentially uninformative messages, marketers should try to gather as much detail as possible from bounce reports to identify patterns or underlying causes. Our article on soft bounces and how to fix them offers general troubleshooting.
Marketer view
An email marketer from Email Geeks indicates that their order confirmation emails, along with other email types, are bouncing to T-Online inboxes when sent through Klaviyo. They note that the bounce messages received are often not very elaborate, making diagnosis difficult.
Marketer view
A marketer from Klaviyo Help Center describes a soft bounce as a temporary delivery failure, for instance, when a recipient's inbox is full or their email server is temporarily down. These types of bounces require monitoring but might resolve on their own.
What the experts say
Email deliverability experts offer critical insights into recurring T-Online bounce issues, often emphasizing the necessity of detailed bounce messages for effective troubleshooting. They highlight that issues on shared IPs within ESPs are a common culprit and stress the importance of direct communication with both the ESP and the receiving ISP. Furthermore, experts underline T-Online's strict requirements concerning technical configurations like DNS records and the presence of proper website contact information.
Key opinions
- Bounce message necessity: Experts universally agree that without the actual bounce message, diagnosing the specific cause of T-Online bounces is extremely difficult, if not impossible.
- Shared IP responsibility: When using a shared IP from an ESP, bounces might not be due to the sender's own practices but rather the actions of other users on the same IP address, suggesting the ESP needs to resolve the issue with the ISP.
- ISP fussiness: T-Online is known to be particularly stringent about various technical and content elements, including DNS configuration (like SPF, DKIM, DMARC) and the sender's website contact information.
- Dedicated IP warmup: It is strongly advised against excluding specific ISPs like T-Online during a dedicated IP warmup, as this prevents the IP from building a complete reputation profile across all major providers.
Key considerations
- Direct engagement with ISP: If bounces persist, experts recommend reaching out directly to the T-Online postmaster or support team to understand their specific requirements or blocklist reasons. They can often provide insights that generic bounce messages do not.
- DNS configuration audit: Thoroughly review your DNS records to ensure they meet T-Online's strict authentication requirements. Misconfigurations in SPF, DKIM, or DMARC can lead to rejections. Our guide on domain does not exist or invalid sender domain errors may offer further insights.
- Website compliance: Ensure your website includes easily findable and complete contact information. Some ISPs (like T-Online) use this as a factor in determining sender legitimacy.
- Patience during warmup: For dedicated IPs, allow time for the IP to build a reputation with all major ISPs by sending consistent volume and maintaining good engagement. Don't avoid sending to any particular ISP during this phase, as this hinders the process. Consult our technical solutions for boosting email deliverability.
Expert view
An expert from Email Geeks strongly advises against excluding T-Online subscribers during the warmup phase for a dedicated IP. They state that such exclusion is unnecessary and can actually hinder the proper establishment of sender reputation with that specific ISP.
Expert view
An expert from SpamResource frequently emphasizes that understanding the specific return codes and messages is paramount for troubleshooting email deliverability issues, as generic 'bounced' notifications offer little actionable intelligence.
What the documentation says
Official documentation from email service providers (ESPs) and general deliverability resources often provide guidelines for interacting with strict ISPs like T-Online. These documents emphasize the importance of list consent, maintaining low bounce rates, and adhering to technical standards (like email authentication). They also offer insights into how ESPs categorize and manage bounces to help senders understand potential issues.
Key findings
- Double opt-in encouraged: Klaviyo strongly recommends keeping double opt-in enabled for all lists by default to comply with strict ISP requirements, particularly for T-Online, to reduce the likelihood of rejections.
- Bounce categorization: Documentation typically differentiates between soft bounces (temporary issues like a full inbox) and hard bounces (permanent issues like an invalid address), with different handling recommendations for each.
- Email deliverability factors: Official guides often list various factors that impact email deliverability, including sender reputation, email content, and recipient server policies, which collectively determine inbox placement.
- Consent is key: Sending to genuinely consented profiles is highlighted as fundamental for reducing bounce rates and improving overall deliverability, as unengaged or invalid addresses lead to rejections.
Key considerations
- Adhere to double opt-in: To satisfy ISPs like T-Online, ensure your list collection methods strictly adhere to double opt-in practices. This verifies subscriber consent and reduces potential spam complaints.
- Monitor bounce types: Pay close attention to the types of bounces (soft vs. hard) reported by your ESP. Hard bounces should result in immediate suppression, while persistent soft bounces may indicate underlying issues or lead to eventual hard bounces. Our guide to T-Online and Arcor.de hard bounces may be useful.
- Regular list hygiene: Implement regular list cleaning processes to remove unengaged or invalid email addresses. This proactive approach helps maintain a healthy sending reputation and reduces future bounce rates.
- Understand deliverability metrics: Familiarize yourself with key email deliverability metrics and how they influence your inbox placement. This includes understanding the factors that ISPs use to assess sender trustworthiness. Learn more about email deliverability issues.
Technical article
Documentation from Klaviyo Help Center states that lists in all Klaviyo accounts are set to double opt-in by default. They strongly recommend keeping this setting enabled to proactively avoid issues with T-Online, as it ensures higher quality subscribers.
Technical article
Documentation from Klaviyo Help Center explains that soft bounces are always caused by a temporary reason, such as a recipient's inbox being full or their email server being momentarily down. This suggests that re-sending might eventually succeed once the temporary condition clears.
Related resources
9 resources
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