I've a stupid confusion, when we say an MTA (mail transport agent) and MDA (mail delivery agent) are responsible for delivering and storing mails then what SMTP server does?
Does an MTA uses SMTP protocol to send
uses an SMTP server that finally sends the mail on request of an MTA or MUA?
PostFix and Sendmail are two implementation of MTA, what are the examples of SMTP server software?
A link to some article that explains all this well, will be a great help.