Deliveryflags, flagtransfer, noflagtransfer Channel Options

Delivery flags
The  channel option may be placed on source or destination channels. It takes a required, bit-encoded integer argument, which controls various options regarding message delivery:

All remaining bits in this option are reserved for internal use and should not be set. The default value for  is 0.

The  channel option may be placed on a SMTP server or LMTP server channel. It causes the server to advertise support of the XDFLG and XAFLG private SMTP/LMTP extension parameters to the RCPT TO command. As of MS 8.0.2.3,  also causes the SMTP server (but not the LMTP server) to advertise the XCONVTAG extension.

If a Messaging Server SMTP client is sending to an SMTP server (or a Messaging Server LMTP client is sending to an LMTP server)  that supports this extension, then that SMTP client (or LMTP client) will pass along (transfer) delivery flags, IMAP flags, and (in the case of SMTP) conversion tags.

For instance, this can be useful when user filters (performing  Sieve operations) will be performed on a "front-line" system that must then relay the messages to a "back-end" system. disables delivery flag transfer and is the default.

Some of the delivery flag bits affect server security, as such, the  channel option should never be set on a channel that is exposed to untrusted traffic.

Setting  is equivalent to setting bit 6 (value 64) of the   channel option.

See also:
 * Sieve discard and jettison actions
 * single Option
 * filter_discard MTA Option
 * filter_discard channel
 * Retrieving messages from the filter_discard channel
 * Sieve fileinto action
 * Typical TCPIP channels and servers
 * CONVERSIONS mapping table
 * Conversion tags
 * Sieve filters and delivery flags channel options
 * Channel options