Form submissions don't appear in Mailchimp Inbox

Description

A user reported that he configured Mailchimp and SMTP2go for the Otter Forms. When he tries to test the service using the designated button, the email is sent to Mailchimp but not to the admin. On the live website, the email is sent to the admin and not to Mailchimp.

I was able to replicate his issue; however, the test email is not appearing in Mailchimp either in my case.

Ref: https://wordpress.org/support/topic/mailchimp-api-with-otter-blocks-contact-form/

Step-by-step reproduction instructions

1. Add the form block
2. Configure Mailchimp
3. Configure an SMTP server (I used WP SMTP email)
4. Paste the API key in the block settings
5. Use the Test Service button in both the Marketing Integration tab and in Advanced from the editor and also check live

Screenshots, screen recording, code snippet or Help Scout ticket

https://www.loom.com/share/1ab3fcc5044e412e84dbb3545f4633d4?sid=87c9eef1-74a1-44cb-8dec-e8d25b3a2d0b

Environment info

No response

Is the issue you are reporting a regression

No

Start with the Otter Forms form block's Mailchimp integration and reproduce the issue using the Test Service button and a live submission, with SMTP configured. Trace the delivery behavior for both the Mailchimp and admin recipients; done means the intended routing is consistent in both test and live flows.