GMAC Loss Mitigation: 1-800-850-4622 Fax: 1-866-502-0424 Letter of Authorization Fax: 1-866-709-4744 Tips for working with GMAC: Make contact as soon as the property is listed for sale.  Send in the letter of authorization and then follow up with a phone call to loss mitigation.  After the authorization letter is processed, they will allow you to [...]