The transmission of DBCS mail by SMTP actually uses two different translation tables, one SBCS and one DBCS. SBCS characters in the mail headers and in the mail body are converted using hlq.STANDARD.TCPKJBIN, TCPHGBIN, TCPSCBIN, or TCPCHBIN.

Both SBCS and DBCS translation tables are required for the transmission of DBCS mail, as the mail can contain mixed-mode strings. A mixed-mode string contains both SBCS and DBCS data, delimited by shift-out and shift-in characters.

DBCS conversion is performed only on outgoing and incoming mail to and from other hosts. Mail spooled to SMTP by SMTPNOTE for the local host is delivered directly, without any DBCS code conversion.