SYMPTOMS

Sending or receiving email fails on the DATA command.

CAUSE

This problem is most likely an issue with the MTU settings of the mail client TCP/IP settings. Windows defaults to a higher frame size than is supported by many routers.

RESOLUTION

The solution is to change the Maximum Transmission Unit (MTU) settings for the IP stack.

This is not specifically a MailEnable problem, but a generic problem/configuration issue with Windows NT when being accessed over hybrid routers.

Use the 'Diagnoses and treatment of black hole routers' article at this link: http://support.microsoft.com/default.aspx?scid=kb%3ben-us%3b159211