Variables

Many filtering decisions depend on how a message arrived rather than on what it says: which client sent it, whether the session was encrypted, whether the sender passed SPF or DMARC. Besides the variables a script defines itself, a Sieve script can therefore read values that describe the SMTP session and the message envelope.

How much a script can read depends on where it runs. System scripts, which run during the SMTP session in the trusted interpreter, see the most. User scripts, which run at delivery in the untrusted interpreter, see the envelope only. Which values exist also depends on the stage at which the script runs, as described in Execution points.

Environment

The session values are read as env.<name>. They can be used in an expression, or in a string with the ${env.<name>} syntax of the variables extension. A value becomes available at the stage where the server learns it, so the DKIM, ARC and DMARC results, for example, exist only at DATA. The following variables are set for system scripts:

Variable	Stages	Value
`env.remote_ip`	all	IP address of the SMTP client.
`env.remote_ip.reverse`	all	The client IP address in reverse notation, for building DNS list queries.
`env.helo_domain`	all, once sent	Domain given in the `EHLO` or `LHLO` command, in lower case.
`env.authenticated_as`	all	Name of the authenticated account, or empty.
`env.asn`	all	Autonomous system number of the client IP address, or `0` when unknown.
`env.country`	all	Country code of the client IP address, when known.
`env.tls.version`	all	TLS version of the connection, empty on a cleartext connection.
`env.tls.cipher`	all	TLS cipher suite of the connection.
`env.stage`	all	The current stage: `connect`, `ehlo`, `mail`, `rcpt` or `data`.
`env.now`	all	Current time, in seconds since the Unix epoch.
`env.spf_ehlo.result`	all	Result of the SPF check of the EHLO domain, empty when no check was made.
`env.spf.result`	all	Result of the SPF check of the MAIL FROM address, empty when no check was made.
`env.iprev.result`	after MAIL FROM	Result of the reverse DNS check, set only when the check ran.
`env.iprev.ptr`	after MAIL FROM	Host name found by the reverse DNS check, in lower case, set only when a PTR record was found.
`env.param.body`	after MAIL FROM	`BODY` parameter of the `MAIL FROM` command: `7bit`, `8bitmime` or `binarymime`.
`env.param.smtputf8`	after MAIL FROM	`1` when the `SMTPUTF8` parameter was given.
`env.param.requiretls`	after MAIL FROM	`1` when the `REQUIRETLS` parameter was given.
`env.dkim.result`	DATA	Result of DKIM verification: the first passing result, otherwise the first result, or empty for an unsigned message.
`env.dkim.domains`	DATA	List of the domains whose DKIM signatures passed verification, in lower case.
`env.arc.result`	DATA	Result of ARC verification.
`env.dmarc.result`	DATA	Result of the DMARC check.
`env.dmarc.policy`	DATA	The DMARC policy of the From domain: `none`, `quarantine` or `reject`.
`env.spam.score`	DATA	Score computed by the spam filter, set only when the filter ran and accepted the message.
`env.spam.is_spam`	DATA	Whether the score reached the spam threshold, set under the same condition.

The authentication results take the values that also appear in the Authentication-Results header, such as pass, fail, softfail, neutral, none, temperror and permerror. A script can therefore test them with the same vocabulary that receivers use. When the spam filter ran at DATA, a system script can also use the spamtest extension.

User scripts have no access to these session variables. Both interpreters do provide the standard values of the environment extension (RFC 5183) through the environment test. Examples are name (Stalwart Server), version, location (MS) and phase (during).

Envelope

The envelope is the addressing information that the SMTP client gives, as distinct from the headers inside the message: the return path and the recipients, with their parameters. It is read with the envelope test, or as envelope.<name> variables. In system scripts, the envelope exists from the MAIL FROM stage onwards, and the recipients accumulate as the session proceeds:

Variable	Value
`envelope.from`	The return path from `MAIL FROM`, in lower case; empty for the null sender `<>`.
`envelope.to`	At MAIL FROM, empty; at RCPT TO, the recipient being added; at DATA, the list of all accepted recipients.
`envelope.orcpt`	The `ORCPT` parameter of the recipients, in the same form as `envelope.to`: one value at RCPT TO, a list in the same order as `envelope.to` at DATA.
`envelope.envid`	The `ENVID` parameter of `MAIL FROM`.
`envelope.ret`	The `RET` parameter of `MAIL FROM`: `FULL` or `HDRS`.
`envelope.by_mode`	The mode of the `BY` parameter of the deliver-by extension: `N` or `R`.

Some envelope variables defined by the Sieve extensions are never set: the NOTIFY parameter (envelope.notify), the deliver-by time values (envelope.by_time_absolute and envelope.by_time_relative) and the trace flag (envelope.by_trace).

A user script runs for a single recipient, so its view of the envelope is narrower. It sees three envelope parts. from is the return path of the message. to is the address of the recipient whose script is running. orcpt is the original recipient, when the sender supplied one.

A user script cannot change the envelope sender. Setting envelope.from has no effect on the message, or on any reply the script sends.