Should the message failed to signup because too many signups really be considered an error?

I agree. It's still an issue in 2.x-dev. We're getting a lot of those "errors" in our logs, which creates a lot of noise.

In this case exposing it as an error makes sense from the Mailchimp API perspective, but for the Drupal module it's not more than a warning and should be logged like this.

According to the Mailchimp API documentation https://mailchimp.com/developer/marketing/docs/errors/ all "Invalid Resource" on subscribe should be validation issues on the Mailchimp end. The MR here prevents logging those into the Drupal logs at all.

Do you think you could add a setting to make this non-logging optional?

No, I don't think it should be an option.

This is an error the Mailchimp API returns, that is in my opinion not an error being relevant for the Drupal site and therefore should not be logged as an error. Drupal errors should be possible to resolve from the site owner. But this validation is kind of spam-protection on the Mailchimp-side we cannot influence. A compromise that I can see is that we log the `Invalid Resource` responses with a different severity, for example warning or info.

What do you think?

Yes, we can definitely reduce the severity.
As far as reducing the frequency, are you using any kind of captcha?

Any kind of Drupal form spam protection can mitigate the issue, yes. In case for example the captcha catches the one that Mailchimp identifies as Spam.

@xenophyle I updated the MR to log the Mailchimp validation errors with a lower severity (notice).

Automatically closed - issue fixed for 2 weeks with no activity.