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Question

Klaviyo and t-online - the massive problem without a real solution (2026)

  • July 9, 2026
  • 2 replies
  • 82 views

Hello.

We left Klaviyo some time ago because you were experiencing massive issues with the T-Online ISP and T-Online mailboxes.


The proposed solutions, workarounds, negative reputation issues, and hard bounce problems were not acceptable to us, which is why we moved away from Klaviyo at that time with more than 60 Klaviyo customer accounts and switched to another service.
 

Unfortunately, your Klaviyo help article regarding Klaviyo and T-Online has been unclear from the very beginning, and there is also significant uncertainty in the forum.
 

The topic of CSA certification has also been officially addressed by you in numerous forum posts, with the promise that you would implement soon it, apply for it, and obtain it. Years later - no solution, nothing happend, no results. No feedback. 
 

To date, neither of these points has been fulfilled nor clearly communicated:

1. Does Klaviyo have a valid CSA certificate, or is a valid CSA certificate expected in the foreseeable future?

Please do not respond with statements such as “we still have a high deliverability rate, please follow the following rules.” We need to know specifically whether the CSA certificate will be available soon and whether the associated benefits can be expected. To set SPF, DMARC and DKIM...this are basics and does not have the same impact what CSA do. Our online shop project customers need a reliable and binding statement on this matter.
 

2. In your documentation regarding T-Online, you state the following here:

https://help.klaviyo.com/hc/de-de/articles/1260804570090

“To meet the requirements of t-online.de for email delivery, there are a few important steps you need to follow. t-online.de has specific requirements that help ensure your emails do not end up in the spam folder. This includes setting up a dedicated sending domain and enabling double opt-in. It is also important that your sender identification is configured correctly in order to avoid bounces.”

We contacted the T-Online postmaster. They stated that this is not a general requirement from T-Online. Instead, these are sender-specific issues that require a dedicated IP at Klaviyo currently and in future.

Other senders do not generally have to meet the dedicated IP requirement.
Question 2: Why you wrote this wrong information to your guide?
 

3. Why does Klaviyo publish this incorrect information? Senders do not generally need to use a dedicated external IP in order to deliver newsletters to T-Online inboxes. The postmaster also confirmed this. At the same time, on Friday, they asked us for the source where we had read this information.

 

4. Klaviyo states this information: Klaviyo states: “T-online.de is an inbox provider primarily used by German subscribers and has unique deliverability requirements. As a result, you may see an increase in bounces from this provider and may no longer be able to reach these German recipients.”

In response, the postmaster stated that this is certainly not the issue and that the problems with Klaviyo have been communicated extensively. So why are these incorrect statements published on your website? The postmaster confirmed: the german location is not the problem.

5. The website mentioned above does not refer to the necessity of a dedicated external IP address, which at the same time requires a very high sending volume in order to build up reputation through sending volume in the first place.

Are we correct in understanding that a dedicated external IP is no longer necessary?

Best regards,
Thomas

 

2 replies

ArpitBanjara
Principal User II
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  • Principal User II
  • July 10, 2026

hello ​@thomas83 

I want to be upfront that I'm not a Klaviyo employee, so I can't give you a binding statement on CSA certification status or speak for what Klaviyo will or won't publish. Those need to come from Klaviyo directly, ideally in writing from your account team or support,, since a community reply from me carries no weight if they later contradict it.

What I can tell you, checked against the live CSA participant list, is that Klaviyo is not currently on it. So your read that this has dragged on for years without resolution is accurate, ,not a misunderstanding on your part.

For the certification timeline and a formal response to why the article's phrasing hasn't been updated despite this being raised repeatedly, that has to go through Klaviyo Support or your account team directly. A community thread, even with a Klaviyo employee replying., isn't the venue for a commitment that legally or operationally binds the company.

I will still tag ​@GabbyEsposito ​@Temi O. ​@Byrne C who should be able to escalate to the right team further.

I hope this helps

Regards
Arpit


Temi O.
Community Manager
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  • Community Manager
  • July 13, 2026

Hi ​@thomas83 , 

thanks for taking the time to lay this out so clearly.

To stay aligned with what Support has already shared, Klaviyo is not currently CSA certified, and there is not an additional public update to share right now around future CSA participation.

On the T-Online side, a dedicated IP is not a universal requirement. The more accurate framing is that double opt-in, sender identification, and authentication alignment are the clearest documented requirements, while a dedicated IP may still be recommended in some cases, particularly for senders with meaningful T-Online volume or ongoing delivery issues.

I completely hear and understand your concern around the wording in the documentation, and I agree that more precision would be helpful here! That feedback has already been shared internally for review.

 


Temi@Klaviyo