# SMTP queue The *smtpd* process implements the [pre-](predelivery.html.md) and [post-delivery](postdelivery.html.md) contexts. These contexts operates on a message in queue. A message in queue is not directly bound to an inbound SMTP connection, hence its delivery is not done inline. ```default ,-------> queue | | <-- Pre-delivery context | delivery attempt | | <-- Post-delivery context \__________/ \______ done ``` * [Pre-delivery](predelivery.html.md) * [Variables](predelivery.html.md#variables) * [Arguments](predelivery.html.md#arguments) * [Queue](predelivery.html.md#queue) * [Plugin](predelivery.html.md#plugin) * [Message](predelivery.html.md#message) * [Id](predelivery.html.md#id1) * [Address](predelivery.html.md#address) * [File](predelivery.html.md#file) * [DSN](predelivery.html.md#dsn) * [Functions](predelivery.html.md#functions) * [`Try()`](predelivery.html.md#Try) * [`Queue()`](predelivery.html.md#Queue) * [`Bounce()`](predelivery.html.md#Bounce) * [`Delete()`](predelivery.html.md#Delete) * [`SetMetaData()`](predelivery.html.md#SetMetaData) * [`GetMetaData()`](predelivery.html.md#GetMetaData) * [On script error](predelivery.html.md#on-script-error) * [On implicit termination](predelivery.html.md#on-implicit-termination) * [Post-delivery](postdelivery.html.md) * [Variables](postdelivery.html.md#variables) * [Arguments](postdelivery.html.md#arguments) * [Policy](postdelivery.html.md#policy) * [Policies](postdelivery.html.md#policies) * [Attempt](postdelivery.html.md#attempt) * [Result](postdelivery.html.md#result) * [Error](postdelivery.html.md#error) * [Connection](postdelivery.html.md#connection) * [TLS](postdelivery.html.md#tls) * [Peercert](postdelivery.html.md#peercert) * [TLSA](postdelivery.html.md#tlsa) * [Records](postdelivery.html.md#records) * [Plugin](postdelivery.html.md#plugin) * [DSN](postdelivery.html.md#dsn) * [Queue](postdelivery.html.md#queue) * [Plugin](postdelivery.html.md#ai1p) * [Message](postdelivery.html.md#message) * [Id](postdelivery.html.md#id2) * [Address](postdelivery.html.md#address) * [File](postdelivery.html.md#file) * [DSN](postdelivery.html.md#dsn2) * [Functions](postdelivery.html.md#functions) * [`Queue()`](postdelivery.html.md#Queue) * [`Bounce()`](postdelivery.html.md#Bounce) * [`Delete()`](postdelivery.html.md#Delete) * [`Default()`](postdelivery.html.md#Default) * [`SetMetaData()`](postdelivery.html.md#SetMetaData) * [`GetMetaData()`](postdelivery.html.md#GetMetaData) * [On script error](postdelivery.html.md#on-script-error) * [On implicit termination](postdelivery.html.md#on-implicit-termination) * [References](postdelivery.html.md#references) * [SMTP states](postdelivery.html.md#smtp-states)