This is not enough to go on and sounds like a support ticket.
Can you describe the email and send us examples? Are you attempting to construct this yourself? Which browser and email client are you using?
It sounds like your internal DNS might be missing the CNAME entries for your landing page and tracking link domains. Some companies have both an internal DNS used by people in the office or on VPN, and an external DNS which is for external users. If the CNAME entries are missing on the internal DNS, it will result in the issues you describe.
I have a little blog post that explains CNAMEs here: Alphabet Soup - CNAME, SPF, and DKIM on your DNS - pt. 1. CNAME
Another way you can test this is to go to any landing page in your Marketo instance and click "View Approved Page" - if the page cannot be found, your landing page CNAME is almost certainly broken.
P.S. The presence of the mkt_tok query param can result in a 404 in some situations (broken webservers). But it won't result in a low-level "site not found" error, because the query string irrelevant to the DNS lookup for the hostname.