|T.37 Option Guide: English 97Network AdministratorService CodesWhen a communication error occurs, print the ActivityReport. Use the report to find the service code for the error.There are two types of service codes. SMTP POP3SMTP Error CodesHere is the format for SMTP communication service codes.E123E = SMTP communication123 = three-digit SMTP error code defined by RFC.RFC is an Internet “standards” term meaning “RequestFor Comment”. RFCs are documents that definestandards or proposed standard-definitions for networkand Internet operation. Individual RFCs define specificaspects of network or Internet operation.Numbers 900 and above are codes defined specifically forthis Internet Fax.
