SMTP (. Simple Mail Transfer Protocol ) , TCP/IP.
ESMTP (. Extended SMTP) SMTP. SMTP, , ESMTP .
SMTP . POP3 IMAP. , , . MX (. Mail eXchange ) DNS. MX , A. SMTP- (, Exim[1]) , , SRV- (RFC 2782). ASCII, , . (, ), ( , , ).
SMTP . <>< >. , , . 100 999, , :
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ESMTP , SMTP. ( EHLO). . , HELO ( SMTP, RFC 821), .
SMTP . , , . SPF, Sender ID. . SPF TXT , , , , email- .
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SPF- DNS-, .
SPF- TXT- DNS:
example.org. IN TXT "v=spf1 +a +mx -all"
v= SPF. : a , IP- IP- A- example.org; mx , MX- example.org. -all , , , .
Sender ID Sender Policy Framework Caller ID. SenderID Email- DNS IP , .
Caller ID , Microsoft , . 24 2004 .
, IP SMTP, , DNS. , IP . IP , .
POP3 (. Post Office Protocol Version 3 , 3) . SMTP.
POP3 3 :
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MAP (. Internet Message Access Protocol ) .
POP3, , , , .
IMAP , . , , , . () . SMTP.
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FTP (. File Transfer Protocol ) , . FTP FTP, ; , (. FXP).
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FTP , HTTP, 1971 . 90- FTP [?]. .
FTP TCP. , . 20 , 21 .
, . FTP, , , , , , FTP . , SSL, FTP- FTP-.
SSL: SSL (. Secure Sockets Layer ) , .
. -( ( , . hashing) . - , , - ). SSL . (, TCP) ( ) (SSL POP3, IMAP, SMTP HTTP). , , , .
-, SSL, URL (schema) http, , https, , SSL-. TCP- https 443.
SSL , , ( , , ..) SSL . SSL, , , .
SSL , SSL-.
FXP (. File eXchange Protocol ) FTP , . FXP , FTP , . , , . FTP (p2p).