Expandable default MTA option

Mailing list and group MTA options:   (0 or 1)
The  MTA option establishes a default for whether lists are expandable; in  particular, it establishes a default for whether the EXPN SMTP command  may be used to expand lists (display list membership).

The default value for this option is 1, meaning that by default lists are  expandable. Note that this default may be overridden on a per list basis. For aliases in Unified Configuration, the  and   alias options override whatever default is set via the   MTA option For lists defined in the aliases file or  alias database, the  &#x5b;EXPANDABLE&#x5d; or &#x5b;NONEXPANDABLE&#x5d; named parameters override whatever default is set via the   MTA option. For lists defined purely in LDAP, the    and   attributes (more precisely, those  attributes named by the   MTA option)  override the  default set via. See also the  channel options.

Also note that for mailing lists with posting access controls, such posting access controls affect when expansion via the  SMTP EXPN command is  allowed; the SMTP server will only permit an EXPN if the SMTP client passes the posting access control (e.g., has issued a prior MAIL FROM: command that passes the access control). Note also that the TCP/IP-channel-specific option   may  be used to disable the EXPN SMTP command entirely for those incoming  TCP/IP channels corresponding to that default TCP/IP channel&#x27;s SMTP  server; see  TCPIP-channel-specific options.

See also:
 * Mailing list and group MTA options
 * expnallow Option
 * DISABLE_EXPAND
 * TCPIP-channel-specific options
 * Alias file named parameters
 * alias_expandable Option
 * alias_nonexpandable Option
 * ldap_expandable MTA Option