I tried using emoneymail.com to send money thus earn FF miles on my visa card, they kept coming back with credit card not authorized, even though my account info is correct. I got a reply from them today on this:

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eMoneyMail seeks to provide customers with a highly secure way to send
money over the Internet. Given the current security concerns with the
Internet, we employ the highest security standards possible to protect
our customers and ensure that fraudulent transactions are minimized.

As a result, while your card may be fine for usage outside of
eMoneyMail, it may not meet the security standards employed by
eMoneyMail. We screen for such things as frequent card usage online,
potential identity manipulation, billing address discrepancies, and
IP address discrepancies.

We apologize if these standards cause you any inconvenience. We hope
you understand our need to protect you and all of our customers from
unauthorized credit card use.

Sincerely,

J.R. McCullough
Operations Manager
eMoneyMail, powered by Bank One