Alias recursion and nested list definitions

Aliases may reference other aliases, in LDAP, in the  alias database, in the  alias file (legacy configuration),  and in    named group Unified Configuration option  settings. To avoid possible infinite recursion reference  loops, the MTA limits such nested or recursive references to a default  maximum of ten levels (see the    MTA option).

If an alias references itself, either directly or indirectly, an alias loop results. The loop eventually terminates due to the level restriction, but the termination conditions may not produce consistent  results in all cases.

The special case of an alias directly referencing itself is allowed and specially handled. For example, the alias file definition alias-name: alias-name, other-address-1, other-address-2, ... will expand  into itself plus  ,   , and so on. may in turn get expanded in some other way (the system alias database or  personal alias database) but it will not be expanded  further by the alias file.

Note that implicit domain name use (having  the MTA itself insert its default domain name onto "bare"  usernames) may affect the "matching" of alias names needed  for the MTA&#x27;s special code to trigger. In order for a "match" to be assured, either use a "bare" username on both the left  and right hand sides, or use a fully-qualified address on both the left  and right hand sides.

See also:
 * max_alias_levels MTA Option
 * Aliases
 * Aliases in LDAP
 * Alias file format
 * Alias database
 * Aliases in Unified Configuration
 * defaulthost Option