How do we associate Amex on our accounts? Thaabit Mollagee November 16, 2018 13:49 Updated Follow Once a merchant receives a merchant number from Amex they would need to send it to firstname.lastname@example.org, and request the Amex merchant number to be associated to their account. Related articles Who do I contact to apply for an American Express Merchant Account? How do I become a 3D secure merchant? Amex Safekey Comments 0 comments Article is closed for comments.