Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z | _1234567890

defer

An action that an MTA receiving an email message can take, which consists of using a 4xx SMTP response code to tell the sending MTA to try again later.