Providing support over the telephone is very expensive (unless you outsource it, and then it's not very good.) In order to provide you the highest quality customer service without price increases, we only provide support via email. Additionally, many customer-specific requests, like "what happened to this message?" require the exact email address, URL or error string -- stuff that is much easier to provide in writing than reading out loud.
While we frequently answer general or system-wide questions via Twitter, account-specific questions should still be sent via email.
If you can't access your email, don't worry. Our customer service ticket system has a web interface. Send us your message here; you'll get a link that you can come back and check for responses. (Or you can give us another email address where we can contact you.)
Corporate accounts can call their sales contacts for additional support.