Jen,
Keep in mind that you would need a method of parsing the email inbox where you receive the messages in order to use the data in some systematic way (for lack of a better word). Marketo does not have the feature to receive emails to auto generate lead entries. And Marketo is not really a CRM. It connects to SFDC which is a CRM but I wouldn't say Marketo itself is a CRM.
As the guys mentioned, if the quality of the data is questionable, I would rather have it stewarded before attempting to bring it into the system whenever possible. One thing you could do is replace the links to the email address with a link to a Marketo capture page. That way you bring them in directly and use the system configuration to route them however you may need.
You can also create a weekly, or daily file from the emails you receive, and copy the data into a CSV file which you could use to import the data into Marketo after it has been stewarded.
Email role accounts (info, webmaster, contact, etc.) tend to get a lot of junk, so perhaps you might also want to consider that as part of your strategy.
Good luck!
Rafael