All the accounts of a customer is getting this error message despite that they all have configured SMTP authentication in their Outlook 2007 clients. Is this an Outlook issue?
Please turn on SMTP Authentication in your mail client. (VENTAS05) [161.132.101.75]:3730 is not permitted to relay through this server without authentication.
Please turn on SMTP Authentication in your mail client. (VENTAS05) [161.132.101.75]:3730 is not permitted to relay through this server without authentication.