Campaign network endpoints
Here are the different endpoints used in Campaign Classic.
https://*.experiencecloud.adobe.com (SSO provider)
https://*.campaign.adobe.com (Campaign Instance)
https://adobeid-na1.services.adobe.com (Adobe login)
Inbox rendering (Litmus)
Branding URL, mirror pages, tracking, fileref (deployment wizard)
Check the URLs that have been configured for you.