A phishing campaign is underway that pretends to be from American Express and states that there is a security issue with your credit card. It then prompts you to open an attached HTML phishing form that will send the inputted information back to the scammers.
Numerous variants have been sent since October 2018. All of these variants utilize the same theme of there being a security review of your credit card that found issues that require you to send your information through an attached form and create a new online account. These emails are being sent out from mail domains that are based off of the “American Express” keyword such as AmExpress@amnex.com, AmericanExpress@ampress.com, and AmericanExpress@aemail.com.
Read more about the phishing campaign on BleepingComputer.