Need quick help with email deliverability

I need quick help with a Klaviyo/email marketing tech issue.

Here’s the gist:

- I started email marketing last year, using Klaviyo, sending from an @firstmoverhealth.com email address. I bought firstmoverhealth.com from Shopify and it’s still a Shopify site. It’s just a basic landing page.

- I started sending messages from this address/domain last year because I knew I was going to start selling some kind of health/wellness product/service in 2026, but didn’t know what yet.

- The email list is people who have opted into hearing from me personally (aka, the domain doesn’t mean anything to them). I always told them I would be launching a product eventually.

- I’m now creating a screen time reduction app for iOS (useexist.com). I bought useexist.com from Cloudfare initially but the site is now hosted in Squarespace.

- I changed the domain inside Klaivyo to useexist.com.

- I just sent my list an email and I told them to reply directly to me if they are interested in testing the iOS app.

- I tried responding to my own message and got this bounce-back (screenshot attached)

I need to make sure I can send messages to my list and get replies without issues.

Can you help?

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