資料一:

三個和email有關的協議:

SMTP simple message transfer protocol:
allow you to send out a message to your internet server
through route to its destination, once it arrives destination
it stored on that mail server until a email client grabs it.

and the two major methods of grabbing that are
IMAP:
Internet Message Access Protocol
(its nice synchronizing two or more applications.
if you have a Blackberry or a Iphone or serveral computers
and you want to read the same message across the board then
IMAP is the system for u.
IMAP allows you to organize a hierachy of messages
so you can have your inbox and then below your inbox
you can have modify folders, sothat all your clients
will get the change of your folders.
if you dont use hierachy organize, pop3 may be better.

if one message you marked as read, all your clients will
show its read.(its all about synchronize
and POP3:
Post Office Protocol Version 3(Quick and simple

資料二:

POP3"

it doesnt download any other folders or their contents,

so it doesnt download your sent items, your drafts,your deleted mail...

and it doesnt do any synchronization

所以可能會造成這樣的問題,新的郵件來了，上面的收到了，但是下面的收不到了，(因為伺服器發給上面的客戶端後就刪除掉了

然而很多客戶端會有一個 leave a copy on the server 選項，防止這種問題發生

IMAP:

如果刪除的時候就是向伺服器發請求 然後其他客戶端會sync

實際客戶端使用的時候是可以配置的:

 或..

優缺點:

pop3 

(因為已經下載到客戶端了

 IMAP:

 (然而 有一些客戶端會有下載到本地 而不是 just caching 的功能

資料三:

POP、IMAP tells where email from

SMTP tells where email to