MailChimp.Net.Core.MailChimpException: akamai_503

We hit an interesting error the other day that doesn't appear to be covered much on Google, so hopefully, this helps someone else.

After sustained attacks on one of our busier sites, we started getting our direct MailChimp API requests rejected with a generic error:

MailChimp.Net.Core.MailChimpException: Title: akamai_503
Type: akamai_error_message
Status: 503
Instance:
Detail:
Errors:
Request URI: https://us14.api.mailchimp.com/3.0/lists/xyz/members/xyz

We use the MailChimp.Net.V3 nuget package, and it had been working fine for well over a year, so we figured it was related to the attacks, but there wasn't much to go on there or on Google.

MailChimp support wasn't aware of the issue and suggested enabling debugging the API calls; we're still waiting on the outcome, but suspect that this happens sooner in the lifecycle, so it wouldn't turn up in their logs.

After a while, we were able to find this IP checker that you can visit from your server, and it'll tell you what reputation you have: https://www.akamai.com/us/en/clientrep-lookup/.

As you can see, we had been flagged as a "Web Attacker" -which is understandable based on the number of fake signups we'd had.

Submitting the request to investigate it with Akamai was a quick and simple process and had us up and running again within a few hours looking at the logs.

Surprisingly the MailChimp client doesn't validate the data being sent -so validate the email addresses before sending them over. We would also recommend debouncing/caching checks where possible to further reduce the calls to the API.