The machine running the application can certainly access Mailchimp (i.e. I can login with a browser) but I'n not sure if MailChimp can access the server. Does the error message mean what it says (i.e. the Mailchimp server cant be reached)... or it is possible that this error message appears when Mailchimp fails to respond?
We've checked the firewall rules and made the additions you suggest but I am still seeing the error message "Could not Access Mailchimp Server". Have you any suggestions as to how to proceed? I was hoping to see something in the SuiteCRM logfile but there's nothing relevant. Can you think of a way that I can diagnose this problem?