Expnallow, expndefault, expndisable Channel Options

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Responding to SMTP EXPN commands (expnallow, expndefault, expndisable)

New in JES MS 6.1: These options control, at a channel level, the SMTP server's response when a sending SMTP client issues an SMTP EXPN command. (These channel options do not apply to or affect LMTP servers.) When placed on a source channel, the expnallow option tells the SMTP server to issue a detailed, informative response. The expndefault tells the SMTP server to provide a detailed, informative response, unless the channel option DISABLE_EXPAND=1 has been specified. The expndisable channel option tells the SMTP server to reject the command with an error:

550 5.7.2 EXPN command has been disabled 

Thus these options allow per-channel control of EXPN responses, as opposed to the DISABLE_EXPAND channel setting which normally applies to all incoming TCP/IP channels handled via the same SMTP server.