SMTP Extensions (EHLO)
After careful consideration, a few extensions have been added to the SMTP protocol
A mailer supporting extensions uses EHLO instead of HELO in the greeting
The server will respond to indicate it can negotiate extensions
If the server gives a failure to the EHLO, the client SMTP reverts back to plain ol’ SMTP
Sometimes called the ‘eight-bit HELO’, but other extensions are included as well