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Internet Message Access Protocol

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Trong may tinh, Internet Message Access Protocol (IMAP) la giao thuc chuan Internet duoc su dung boi cac ung dung email de truy xuat thu email tu may chu thu qua ket noi TCP/IP.[1] IMAP duoc xac dinh boi RFC 3501.

IMAP duoc thiet ke voi muc tieu cho phep quan ly hoan toan hop thu email cua nhieu khach hang email, do do, khach hang thuong de lai thu tren may chu cho den khi nguoi dung xoa chung mot cach ro rang. Mot may chu IMAP thuong lang nghe tren cong so 143. IMAP qua SSL (IMAPS) duoc gan so cong 993.

Hau nhu tat ca cac may khach va may chu email hien dai deu ho tro IMAP, cung voi POP3 (Post Office Protocol) truoc do la hai giao thuc tieu chuan pho bien nhat de truy xuat email.[2] Nhieu nha cung cap dich vu webmail nhu Gmail, Outlook.com va Yahoo! Mail cung cung cap ho tro cho IMAP hoac POP3.

Giao thuc thu dien tu

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Giao thuc truy cap thu Internet la mot giao thuc Internet cua lop ung dung cho phep may khach email truy cap email tren may chu thu tu xa. Phien ban hien tai duoc xac dinh boi RFC 3501. Mot may chu IMAP thuong lang nghe tren cong 143 noi tieng, trong khi IMAP qua SSL (IMAPS) su dung 993.

Tin nhan e-mail den duoc gui den mot may chu e-mail luu tru tin nhan trong hop e-mail cua nguoi nhan. Nguoi dung truy xuat cac thu voi ung dung khach email su dung mot trong so cac giao thuc truy xuat email. Mac du mot so khach hang va may chu uu tien su dung cac giao thuc doc quyen, danh rieng cho nha cung cap,[3] hau nhu tat ca deu ho tro POP va IMAP de truy xuat email - cho phep nhieu lua chon mien phi giua nhieu ung dung khach email nhu Pegasus Mail hoac Mozilla Thunderbird de truy cap cac may chu nay va cho phep cac may khach duoc su dung voi cac may chu khac.

Cac ung dung email khach su dung IMAP thuong de lai tin nhan tren may chu cho den khi nguoi dung xoa chung mot cach ro rang. Dieu nay va cac dac diem khac cua hoat dong IMAP cho phep nhieu khach hang quan ly cung mot hop thu. Hau het cac ung dung khach email deu ho tro IMAP ngoai Post Office Protocol (POP) de truy xuat thu.[4] IMAP cung cap quyen truy cap vao bo luu tru thu. Khach hang co the luu tru cac ban sao cuc bo cua tin nhan, nhung chung duoc coi la bo dem tam thoi.[5]

Lich su

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IMAP duoc Mark Crispin thiet ke vao nam 1986 nhu mot giao thuc hop thu truy cap tu xa, trai nguoc voi POP duoc su dung rong rai, mot giao thuc chi don gian la lay noi dung cua hop thu.

No da trai qua mot so phien ban truoc VERSION 4rev1 (MAPI4) hien tai, nhu chi tiet duoi day:

IMAP ban dau

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Interim Mail Access Protocol ban dau duoc trien khai duoi dang may khach Xerox Lisp va may chu TOPS-20.

Khong co ban sao cua dac ta giao thuc tam thoi goc hoac phan mem cua no ton tai.[6][7] Mac du mot so lenh va phan hoi cua no tuong tu IMAP2, giao thuc tam thoi thieu gan the lenh / phan hoi va do do cu phap cua no khong tuong thich voi tat ca cac phien ban IMAP khac.

IMAP2

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Giao thuc tam thoi nhanh chong duoc thay the bang Interactive Mail Access Protocol (IMAP2), duoc xac dinh trong RFC 1064 (nam 1988) va sau do duoc cap nhat boi RFC 1176 (nam 1990). IMAP2 da gioi thieu gan the lenh / phan hoi va la phien ban phan phoi cong khai dau tien.

IMAP3

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IMAP3 la mot bien the cuc ky hiem cua IMAP.[8] No duoc xuat ban voi ten RFC 1203 vao nam 1991. No duoc viet cu the nhu mot de xuat phan doi voi RFC 1176, chinh no da de xuat sua doi cho IMAP2.[9] IMAP3 khong bao gio duoc chap nhan boi thi truong.[10][11] IESG phan loai lai RFC1203 "Giao thuc truy cap thu tuong tac - Phien ban 3" nhu mot giao thuc Lich su vao nam 1993. Nhom lam viec IMAP da su dung RFC1176 (IMAP2) thay vi RFC1203 (IMAP3) lam diem bat dau.[12][13]

IMAP2bis

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Voi su ra doi cua MIME, IMAP2 da duoc mo rong de ho tro cau truc doi tuong MIME va them chuc nang quan ly hop thu (tao, xoa, doi ten, tai len tin nhan) khong co trong IMAP2. Ban sua doi thu nghiem nay duoc goi la IMAP2bis; dac diem ky thuat cua no da khong bao gio duoc cong bo o dang khong du thao. Mot ban nhap cua IMAP2bis da duoc Nhom lam viec IETF IMAP xuat ban vao thang 10 nam 1993. Du thao nay dua tren cac thong so ky thuat truoc day: IMAP2bis chua duoc cong bo . Tai lieu TXT, RFC1176 va RFC1064 (IMAP2).[14] IMAP2bis. Ban nhap TXT da ghi lai trang thai cua cac phan mo rong cho IMAP2 ke tu thang 12 nam 1992.[15] Cac phien ban dau tien cua Thong duoc phan phoi rong rai voi ho tro IMAP2bis [8] (Pine 4 va sau do ho tro IMAP4rev1).

IMAP4

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Mot nhom lam viec IMAP duoc thanh lap trong IETF vao dau nhung nam 1990 da chiu trach nhiem ve thiet ke IMAP2bis. WG IMAP da quyet dinh doi ten IMAP2bis thanh IMAP4 de tranh nham lan.

Uu diem so voi POP

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Che do ket noi va ngat ket noi

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Khi su dung POP, khach hang thuong ket noi nhanh voi may chu email, chi khi can tai xuong thu moi. Khi su dung IMAP4, khach hang thuong duy tri ket noi mien la giao dien nguoi dung duoc kich hoat va tai xuong noi dung tin nhan theo yeu cau. Doi voi nguoi dung co nhieu hoac nhieu tin nhan, mau su dung IMAP4 nay co the dan den thoi gian phan hoi nhanh hon.

Nhieu khach hang dong thoi

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Giao thuc POP yeu cau may khach hien duoc ket noi la may khach duy nhat duoc ket noi voi hop thu. Nguoc lai, giao thuc IMAP dac biet cho phep truy cap dong thoi boi nhieu khach hang va cung cap cac co che de khach hang phat hien cac thay doi duoc thuc hien doi voi hop thu bang cac may khach khac, duoc ket noi dong thoi. Xem vi du RFC3501 phan 5.2 trong do trich dan cu the "truy cap dong thoi vao cung mot hop thu boi nhieu tac nhan" lam vi du.

Truy cap vao phan tin nhan MIME va tim nap mot phan

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Thong thuong tat ca e-mail Internet duoc truyen o dinh dang MIME, cho phep cac tin nhan co cau truc cay trong do cac nut la la bat ky loai noi dung mot phan nao va cac nut khong co la la bat ky loai da dang nao. Giao thuc IMAP4 cho phep khach hang truy xuat bat ky phan MIME rieng le nao va cung co the truy xuat cac phan cua tung phan rieng le hoac toan bo tin nhan. Cac co che nay cho phep khach hang truy xuat phan van ban cua tin nhan ma khong can truy xuat cac tep dinh kem hoac truyen phat noi dung khi no dang duoc tim nap.

Thong tin trang thai tin nhan

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Thong qua viec su dung cac co duoc xac dinh trong giao thuc IMAP4, khach hang co the theo doi trang thai tin nhan: vi du: tin nhan da duoc doc, tra loi hay xoa. Cac co nay duoc luu tru tren may chu, vi vay cac may khach khac nhau truy cap vao cung mot hop thu vao cac thoi diem khac nhau co the phat hien cac thay doi trang thai duoc thuc hien boi cac may khach khac. POP khong cung cap co che cho khach hang luu tru thong tin trang thai nhu vay tren may chu, vi vay neu mot nguoi dung truy cap hop thu co hai ung dung khach POP khac nhau (vao cac thoi diem khac nhau), thong tin trang thai, chang han nhu lieu tin nhan da duoc truy cap co the duoc dong bo hoa giua khach hang Giao thuc IMAP4 ho tro ca co he thong duoc xac dinh truoc va tu khoa do khach hang xac dinh. Co he thong cho biet thong tin trang thai nhu tin nhan da duoc doc chua. Tu khoa, khong duoc ho tro boi tat ca cac may chu IMAP, cho phep tin nhan duoc cung cap mot hoac nhieu the co y nghia tuy thuoc vao may khach. Khong nen nham lan tu khoa IMAP voi nhan doc quyen cua dich vu email dua tren web doi khi duoc dich sang thu muc IMAP boi cac may chu doc quyen tuong ung.

Nhieu hop thu tren may chu

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May khach IMAP4 co the tao, doi ten va/hoac xoa hop thu (thuong duoc hien thi cho nguoi dung duoi dang thu muc) tren may chu va sao chep thu giua cac hop thu. Ho tro nhieu hop thu cung cho phep cac may chu cung cap quyen truy cap vao cac thu muc chung va chung. Phan mo rong Danh sach kiem soat truy cap IMAP4 (ACL) (RFC 4314) co the duoc su dung de dieu chinh quyen truy cap.

Tim kiem phia may chu

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IMAP4 cung cap mot co che de khach hang yeu cau may chu tim kiem cac thu dap ung nhieu tieu chi khac nhau. Co che nay tranh yeu cau khach hang tai xuong moi thu trong hop thu de thuc hien cac tim kiem nay.

Co che mo rong tich hop

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Phan anh trai nghiem cua cac giao thuc Internet truoc do, IMAP4 xac dinh mot co che ro rang ma theo do no co the duoc mo rong. Nhieu phan mo rong IMAP4 cho giao thuc co so da duoc de xuat va duoc su dung pho bien. IMAP2bis khong co co che mo rong va POP hien co mot co che duoc xac dinh boi RFC 2449.

Nhuoc diem

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Mac du IMAP khac phuc duoc nhieu thieu sot cua POP, nhung dieu nay von da gioi thieu su phuc tap bo sung. Phan lon su phuc tap nay (vi du: nhieu may khach truy cap cung mot hop thu cung mot luc) duoc bu dap bang cac cach giai quyet phia may chu nhu Maildir hoac phu tro co so du lieu.

Dac ta IMAP da bi chi trich la khong du nghiem ngat va cho phep cac hanh vi phu nhan tinh huu dung cua no mot cach hieu qua. Chang han, thong so ky thuat noi rang moi tin nhan duoc luu tru tren may chu co mot "id duy nhat" de cho phep khach hang xac dinh cac tin nhan ma ho da thay giua cac phien. Tuy nhien, dac diem ky thuat cung cho phep cac UID nay bi vo hieu ma khong bi han che, thuc te da danh bai muc dich cua chung.[16]

Tru khi cac thuat toan luu tru va tim kiem thu tren may chu duoc trien khai can than, khach hang co kha nang tieu thu mot luong lon tai nguyen may chu khi tim kiem cac hop thu lon.

Cac may khach IMAP4 can duy tri ket noi TCP / IP den may chu IMAP de duoc thong bao ve su xuat hien cua thu moi. Thong bao ve viec gui thu duoc thuc hien thong qua bao hieu trong bang tan, dieu nay gop phan vao su phuc tap cua viec xu ly giao thuc IMAP phia khach hang.[17] Mot de xuat rieng, day IMAP, se mo rong IMAP de trien khai e-mail day bang cach gui toan bo thu thay vi chi mot thong bao. Tuy nhien, viec day IMAP thuong khong duoc chap nhan va cong viec IETF hien tai da giai quyet van de theo nhung cach khac (xem Ho so Lemonade de biet them thong tin).

Khong giong nhu mot so giao thuc doc quyen ket hop cac hoat dong gui va truy xuat, gui tin nhan va luu mot ban sao trong thu muc phia may chu voi ung dung khach IMAP cap co so yeu cau truyen noi dung thu hai lan, mot lan den SMTP de gui va lan thu hai den IMAP luu tru trong mot thu muc thu da gui. Dieu nay duoc giai quyet bang mot bo tien ich mo rong duoc xac dinh boi IETF Lemonade Profile cho thiet bi di dong: URLAUTH (RFC 4467) va CATENATE (RFC 4469) trong IMAP va BURL (RFC 4468) trong SMTP-SUBMISSION. Ngoai ra, Courier Mail Server cung cap mot phuong thuc gui khong chuan bang IMAP bang cach sao chep thu di vao thu muc hop thu di chuyen dung.[18]

Bao mat

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De bao mat bang mat ma cac ket noi IMAP, IMAPS tren cong TCP 993 co the duoc su dung, su dung TLS. Ke tu RFC 8314, day la co che duoc khuyen nghi.

Ngoai ra, STARTTLS co the duoc su dung de cung cap lien lac an toan giua MUA giao tiep voi MSA hoac MTA thuc hien Giao thuc SMTP.

Vi du ve hop thoai

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Day la mot ket noi IMAP vi du nhu duoc lay tu RFC 3501 phan 8:

C:
S: * OK IMAP4rev1 Service Ready
C: a001 login mrc secret
S: a001 OK LOGIN completed
C: a002 select inbox
S: * 18 EXISTS
S: * FLAGS (\Answered \Flagged \Deleted \Seen \Draft)
S: * 2 RECENT
S: * OK [UNSEEN 17] Message 17 is the first unseen message
S: * OK [UIDVALIDITY 3857529045] UIDs valid
S: a002 OK [READ-WRITE] SELECT completed
C: a003 fetch 12 full
S: * 12 FETCH (FLAGS (\Seen) INTERNALDATE "17-Jul-1996 02:44:25 -0700"
RFC822.SIZE 4286 ENVELOPE ("Wed, 17 Jul 1996 02:23:25 -0700 (PDT)"
"IMAP4rev1 WG mtg summary and minutes"
(("Terry Gray" NIL "gray" "cac.washington.edu"))
(("Terry Gray" NIL "gray" "cac.washington.edu"))
(("Terry Gray" NIL "gray" "cac.washington.edu"))
((NIL NIL "imap" "cac.washington.edu"))
((NIL NIL "minutes" "CNRI.Reston.VA.US")
("John Klensin" NIL "KLENSIN" "MIT.EDU")) NIL NIL
"")
BODY ("TEXT" "PLAIN" ("CHARSET" "US-ASCII") NIL NIL "7BIT" 3028
92))
S: a003 OK FETCH completed
C: a004 fetch 12 body[header]
S: * 12 FETCH (BODY[HEADER] {342}
S: Date: Wed, 17 Jul 1996 02:23:25 -0700 (PDT)
S: From: Terry Gray
S: Subject: IMAP4rev1 WG mtg summary and minutes
S: To: imap@cac.washington.edu
S: cc: minutes@CNRI.Reston.VA.US, John Klensin
S: Message-Id:
S: MIME-Version: 1.0
S: Content-Type: TEXT/PLAIN; CHARSET=US-ASCII
S:
S:)
S: a004 OK FETCH completed
C a005 store 12 +flags \deleted
S: * 12 FETCH (FLAGS (\Seen \Deleted))
S: a005 OK +FLAGS completed
C: a006 logout
S: * BYE IMAP4rev1 server terminating connection
S: a006 OK LOGOUT completed

Tham khao

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  1. ^ Dean, Tamara (2010). Network+ Guide to Networks. Delmar. tr. 519. ISBN 1423902459.
  2. ^ Komarinski, Mark (2000). Red Hat Linux System Administration Handbook. Prentice Hall. tr. 179. ISBN 1423902459.
  3. ^ Vi du, Microsoft 's Outlook client su dung MAPI, mot Microsoft giao thuc doc quyen, de giao tiep voi mot Microsoft Exchange Server. May khach Ghi chu cua IBM hoat dong theo cach tuong tu khi giao tiep voi may chu Domino.
  4. ^ Mullet, Diana (2000). Managing IMAP. O'Reilly. tr. 25. ISBN 0-596-00012-X.
  5. ^ See e.g. Timo Sirainen, Dave Cridland. "IMAP Client Coding HOWTO". Ban goc luu tru ngay 7 thang 7 nam 2017. Truy cap ngay 19 thang 3 nam 2019.
  6. ^ Crispin, Mark (ngay 13 thang 2 nam 2012). "Re: [imap5] Designing a new replacement protocol for IMAP". imap5 (Danh sach thu). Truy cap ngay 26 thang 11 nam 2014. Knowledge of the original IMAP (before IMAP2) exists primarily in my mind as all the original IMAP specifications and implementations were replaced with IMAP2. {{Chu thich danh sach thu}}: Da bo qua tham so khong ro |mailinglist= (goi y |mailing-list=) (tro giup)
  7. ^ Ten dich vu va dang ky giao thuc so cong giao thuc. Iana.org (2013-07-12). Truy cap ngay 2013/07/17.
  8. ^ a b "RFC 2061 - IMAP4 COMPATIBILITY WITH IMAP2BIS". IETF. 1996. Truy cap ngay 21 thang 8 nam 2010.
  9. ^ "INTERACTIVE MAIL ACCESS PROTOCOL - VERSION 3". IETF. 1991. Truy cap ngay 21 thang 8 nam 2010.
  10. ^ "IMAP2, IMAP2bis, IMAP3, IMAP4, IMAP4rev1 (LAN Mail Protocols)". Truy cap ngay 21 thang 8 nam 2010.
  11. ^ "IMAP Overview, History, Versions and Standards". Truy cap ngay 21 thang 8 nam 2010.
  12. ^ "Protocol Action: Interactive Mail Access Protocol -- Version 3 to Historic (IETF mail archive)". 1993. Truy cap ngay 21 thang 8 nam 2010.
  13. ^ "Innosoft and POP/IMAP protocols? (mail archive)". 1993. Truy cap ngay 21 thang 8 nam 2010.
  14. ^ "INTERACTIVE MAIL ACCESS PROTOCOL - VERSION 2bis (Internet Draft)". IETF. 1993. Truy cap ngay 21 thang 8 nam 2010.
  15. ^ "IMAP2BIS -- EXTENSIONS TO THE IMAP2 PROTOCOL (DRAFT)". 1992. Ban goc luu tru ngay 18 thang 7 nam 2011. Truy cap ngay 21 thang 8 nam 2010.
  16. ^ "IMAP implementation in Sup, an e-mail client written in Ruby". rubyforge.com. Ban goc luu tru ngay 12 thang 12 nam 2007. Truy cap ngay 22 thang 2 nam 2011.
  17. ^ "IMAP IDLE: The best approach for 'push' e-mail". Isode.com. Ban goc luu tru ngay 28 thang 2 nam 2009. Truy cap ngay 30 thang 7 nam 2009.
  18. ^ "Courier-IMAP: Sending mail via an IMAP connection". Double Precision, Inc. Truy cap ngay 24 thang 9 nam 2013.

Lien ket ngoai

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