SMTP client class is a PHP class that connects to a mail server to send messages. It can relay message delivery to a defined server or directly deliver messages to a recipient's server for urgent message delivery. It supports secure connections with SSL or starting TLS after the connection is established, connection timeouts, authentication using PHP SASL class (PLAIN, LOGIN, CRAM-MD5, NTLM), POP3 before SMTP delivery authentication, and takes advantage of the SMTP PIPELINING extension to buffer SMTP commands, providing much faster queueing of messages when delivering to a large number of recipients (bulk mail).
