Internet Direct (Indy) Version 9.0.2 Beta
TIdSMTPServerThread.EHLO
Indicates if the SMTP client has identified itself, and requested SMTP service extensions for the SMTP session.

EHLO: Boolean;
Description
EHLO is a public Boolean member that indicates if the SMTP client connection has supplied an EHLO client identification command, which contains a fully-qualified domain name, to initiate the SMTP session. When EHLO is True, this indicates that the SMTP client is able to process SMTP server extensions, and requests that the SMTP server provide a list of the extensions in its implementation.

Older SMTP systems which are unable to support SMTP service extensions, and clients which do not require service extensions in the mail session, may use HELO instead of EHLO.

EHLO is used in the command action handlers for SMTP commands that require a valid session prior to starting a mail transaction, like MAIL, RCPT, and DATA.

EHLO is also used in the command action handler for SMTP AUTH command to determine if authentication is performed using the internal implementation, or the TBasicHandler event handler OnCommandAUTH for the threaded SMTP client connection. When EHLO Is True and OnCommandAUTH has an assigned procedure, the event handler is used to perform authentication instead of the internal server implementation.

EHLO is updated in the command action handler CommandEHLO. Note: The EHLO command action handler will set the value of both HELO and EHLO to True on successful completion of the handler when the server indicates that EHLO is supported in AllowEHLO.