I have a client who switched ISPs from Comcast to Verizon. They can receive mail but not send.
They get an “You do not have permission to send to this recipient. For assistance, contact your system administrator. #5.7.1 smtp;550 5.7.1 Authentication Required>” error when trying to send.
I put in an SMTP virtual server entry for Verizon’s outgoing mail server…but Verizon also says I may need to provide the user’s login credentials in the server for authentication. I can’t find where to put in these credentials into Exchange and Verizon could not tell me either…can someone here help??
