I would not send this much information without a secure online payment method. There is no reason that the mmn is needed for a cc transaction by a merchant. It is used to authenticate you when you call, but it is NEVER needed for a transaction. We recently paid a deposit for fall trip to Africa with an American operator. We signed the cc authorization forms with our signatures and no credit card information and scanned those. We then called in the credit card numbers so they were not sent over an non secure internet connection. Not only were there no issues, they were very accomodating, and said that many people will not scan the authorization forms with all the information filled in. Alternatively you can have a password protected pdf created which at least provides a minimum level of security.