Deliverability issue and big bounce spike

It looks like Gmail has blocked your emails in the second campaign, leading to a massive spike in soft bounces. Here are some possible reasons and solutions:

Possible Causes:

1. Reputation Issues: If Gmail flagged your domain/IP as suspicious due to high sending volume or engagement drop, it may have temporarily blocked your emails.
2. Spam Filter Sensitivity: If your second campaign had different wording, images, or links, it might have triggered Gmail's spam filters.
3. Sudden Volume Increase: If Gmail detected an unusual pattern (e.g., sending to the same large list repeatedly in a short time), it may have limited delivery.
4. Email Authentication Issues: If your SPF, DKIM, or DMARC records are misconfigured or have changed, Gmail may reject your emails.
5. Engagement Decline: If recipients didn’t open or engaged less with the first campaign, Gmail may have deprioritized the second one.

How to Fix It:

✅ Check Gmail’s Postmaster Tools – See if your domain has reputation issues.
✅ Analyze Your Bounce Messages – Look for any patterns or reasons provided by Gmail.
✅ Authenticate Your Emails – Verify SPF, DKIM, and DMARC settings are correct.
✅ Warm Up Your IP – If you’ve recently changed email providers or increased volume, warm up your domain gradually.
✅ Adjust Frequency & Content – Avoid sending identical campaigns too frequently to the same list.
✅ Clean Your List – Remove inactive emails and avoid sending to unengaged subscribers.

If you can share the exact bounce reason Gmail provided, I can help interpret it better! 

Hi ​@yoana.f, welcome to the community!

From the screenshot you shared, the errors seem to indicate you haven’t properly setup your Sender Requirements.  Klaviyo has a guide here that briefly explains what it means and what you need to do step by step:

• How to meet Google and Yahoo's email sender requirements in 2024

Specifically, you need to make sure your have you DMARC policy properly configured after you set up your branded sending domain. Give that a try and let us know if it helped.

This error is indicating that your DMARC settings are not aligned with the updated requirements from Google as of February 2024. You will need to make this changes via DNS.

In addition to this you can also consider using a dedicated sending IP to improve deliverability, and to hedge against other IP’s ruining your domain reputation.

You can use the deliverability settings inside your Klaviyo instance or google postmaster to check various deliverability metrics.