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Comparators

Comparators are functions that evaluate the contents of a variable against a specified value and return a boolean result. The following value comparators are available:

  • eq / ne: Tests for equality / non-equality of the value.
  • starts-with / not-starts-with: Tests whether a string starts with / does not start with a specified value.
  • ends-with / not-ends-with: Tests whether a string ends with / does not end with a specified value.
  • in-list / not-in-list: Tests whether a value is present / not present in a directory.
  • matches / not-matches: Tests whether a value matches a regular expression / does not match a regular expression.

Lookup Lists​

Lookups allow the evaluation of queries against a SQL database, LDAP directory or local lists. Lookups are useful for validating recipients, authenticating accounts, verifying addresses, expanding mailing lists or checking the presence of a value in a table. Queries and lists are defined under the directory.<name>.lookup.<lookup_name> section of the configuration file, where <name> is the identifier of the directory and <lookup_name> is the name of the lookup. To reference a lookup from a rule, use the in-list = "<name>/<lookup_name>" comparator to check if a value is contained in the lookup list.

For example, the following configuration defines a lookup named trusted_ips that checks if the remote IP address is present in the trusted_ips table of a mySQL database:

[directory."mysql".lookup]
trusted_ips = "SELECT 1 FROM trusted_ips WHERE address=? LIMIT 1"

[session.rcpt]
relay = [ { any-of = [ { if = "remote-ip", in-list = "mysql/trusted_ips" },
                       { if = "authenticated-as", ne = "" }], then = true }, 
          { else = false } ]

Lookup lists can also be defined in the configuration file using the memory directory type under the directory.<name>.lookup.<lookup_name> section. For example:

[directory."lists"]
type = "memory"

[directory."lists".lookup]
can_vrfy = ["[email protected]", "[email protected]"]

[session.extensions]
vrfy = [ { if = "authenticated-as", in-list = "lists/can_vrfy", then = true},
        { else = false } ]

Strings​

Variables such as sender or rcpt that contain string values can be evaluated using any of the value comparators, for instance:

max-recipients = [ { if = "sender", matches = "^(.+)@(.+)$", then = 20 },
                   { if = "authenticated-as", starts-with = "john@", then = 1000 },
                   { if = "sender-domain", in-list = "db/postgresql/paid_clients", then = 5000 },
                   { else = 5 } ]

Integers​

Variables such as priority that contain integer values can be evaluated only using the equality or list comparators, for instance:

expire = [ { if = "priority", eq = "1", then = "5d" },
           { if = "priority", in-list = "list/low_priorities", then = "1d" },
           { else = "3d" } ]

IP Addresses​

Variables such as remote-ip or local-ip that contain IP addresses can be evaluated using the equality or list comparators. When using the equality comparator, IP ranges may be specified using CIDR notation, for instance:

notify = [ { if = "remote-ip", eq = "198.51.100.0/22", then = ["1d", "2d", "3d"] },
           { if = "remote-ip", in-list = "list/lmtp_hosts", then = ["30d"] },
           { if = "local-ip", ne = "2001:db8::/48", then = ["4d"] },
           { else = ["5d", "6d"] } ]