Just to update and stay still not working for me. I have had Hostgatgor look into this, and they have said basically there are two choices – either move my websites to VPS or dedicated hosting account – or find another host.
They do also suggest asking you the plugin developer or going back to Mailchimp and asking them to unblock the IP my site is on (which is a shared server)
But to confirm this issue is as you say Mailchimp blocking certain servers – and of course if you are on a shared server, like my site is, then you stand a risk of another user getting your server blacklisted
here’s the response from my host (Hotgator) if useful to anyone
Hello,
It looks as though the server’s main IP, 192.185.2.19 has been blocked:
[~]# curl -I –interface 192.185.2.19 https://us2.api.mailchimp.com/2.0/
HTTP/1.0 400 Bad Request
Server: AkamaiGHost
Mime-Version: 1.0
Content-Type: text/html
Content-Length: 297
Expires: Mon, 19 Oct 2015 21:00:20 GMT
Date: Mon, 19 Oct 2015 21:00:20 GMT
Connection: close
However, other IPs on the server don’t appear to be affected:
[~]# curl -I –interface 192.185.3.28 https://us2.api.mailchimp.com/2.0/
HTTP/1.1 200 OK
Server: nginx
Content-Type: text/xml; charset=utf-8
Vary: Accept-Encoding
Date: Mon, 19 Oct 2015 21:00:05 GMT
Content-Length: 0
Connection: keep-alive
Set-Cookie: _AVESTA_ENVIRONMENT=prod; path=/
[~]# curl -I –interface 192.185.3.5 https://us2.api.mailchimp.com/2.0/
HTTP/1.1 200 OK
Server: nginx
Content-Type: text/xml; charset=utf-8
Vary: Accept-Encoding
Date: Mon, 19 Oct 2015 21:01:17 GMT
Content-Length: 0
Connection: keep-alive
Set-Cookie: _AVESTA_ENVIRONMENT=prod; path=/
This is relevant because no matter what IP an account is on, it will by default use the server’s main IP to send external requests. Because of this, one possible solution in this case would see to be if the MailChimp plugin can be altered to send from one of the un-blocked IPS. This is also important because it means changing an account IP will not help in this situation, because again outbound traffic by default goes from the main server IP, which appears to be the blocked one.
If you are unable to change the settings for that Mailchimp for WordPress plugin to use any IP other than the main server IP, your only recourse will likely be to consider migration to a VPS or dedicated server. The reason for this being that those type of hosting packages are not shared with other users, and therefore IP reputation will be dependent on the activity of you and your users alone.
You are quite correct that this entails any account on this server will have the same problem, unless the application can be configured to bind to one of the non-blocked IPs. Getting a dedicated IP will not help in a shared hosting context either for this same reason.
So to sum up, the options you have as I see them would be to see if MailChimp can help you send requests from a different non-blocked IP on the server, or else consider migrating to a dedicated or VPS server in which the IP reputation won’t be affected by other users.
If you have any further questions or concerns, please let us know.
Best Regards,
Dale M,
Linux Administrator