Microsoft Outlook stores your emails, tasks, and appointments as either PST or OST files. These both do the same basic job. However, there are some differences that are important, depending on whether you want to backup, restore, or move your data.

Microsoft Outlook將您的電子郵件，任務和約會儲存為PST或OST檔案。 這些都做相同的基本工作。 但是，有些差異很重要，具體取決於您是要備份，還原還是移動資料。

To explain the difference between PST and OST files, we have to explain a bit of technological history—specifically, the difference between the POP and IMAP email protocols. Here’s a quick overview.

為了解釋PST和OST檔案之間的區別，我們必須解釋一些技術歷史，特別是POP和IMAP電子郵件協議之間的區別。 這是一個快速概述。

什麼是POP？ (What Is POP?)

The traditional email protocol used in dial-up times was Post Office Protocol (POP). The current version of POP is version 3 (POP3).

撥號時間使用的傳統電子郵件協議是郵局協議(POP)。 POP的當前版本是版本3(POP3)。

POP downloaded all your emails to the client, and then, by default, deleted them from the email server. This meant only a copy of your emails was on your computer. You could configure POP not to delete emails from the server.

POP將所有電子郵件下載到客戶端，然後預設情況下將其從電子郵件伺服器中刪除。 這意味著您的計算機上只有電子郵件的副本。 您可以將POP配置為不從伺服器刪除電子郵件。

However, in those days, people normally checked their email from only one computer, so there wasn’t really a need to keep a second copy on the server.

但是，在那些日子裡，人們通常只從一臺計算機檢查電子郵件，因此實際上並不需要在伺服器上保留第二份副本。

When you use POP, any changes you make in your email client aren’t reflected in the email server. If you delete an email in the email client, nothing happens on the email server, and vice versa.

使用POP時，您在電子郵件客戶端中進行的任何更改都不會反映在電子郵件伺服器中。 如果在電子郵件客戶端中刪除電子郵件，則電子郵件伺服器上不會發生任何React，反之亦然。

什麼是IMAP？ (What Is IMAP?)

Internet Messaging Access Protocol (IMAP) is a more modern protocol that downloads a copy of your email from the server to the client on your computer. Any changes you make in your email client are synced with the server. If you delete an email on your computer, it’s also deleted on the email server, and vice versa.

Internet訊息訪問協議(IMAP)是一種更現代的協議，可以將電子郵件的副本從伺服器下載到計算機上的客戶端。 您在電子郵件客戶端中所做的任何更改都將與伺服器同步。 如果您在計算機上刪除電子郵件，則電子郵件伺服器上的電子郵件也會被刪除，反之亦然。

IMAP is much more suited to the modern world. We now access the same email account on multiple devices and most people have “always-on” broadband or fiber connections, and mobile data. Everything you do with your email is synced if you use IMAP.

IMAP更適合現代世界。 現在，我們可以在多個裝置上訪問同一電子郵件帳戶，並且大多數人擁有“始終線上”的寬頻或光纖連線以及移動資料。 如果使用IMAP，則對電子郵件所做的所有操作都會同步。

For example, if you send an email from your phone, you can look in the “Sent” folder on your tablet, and the email you sent will be there, as well. This is why we recommend using IMAPunless you have a specific reason to use POP3.

例如，如果您通過手機發送電子郵件，則可以在平板電腦上的“已傳送”資料夾中查詢，傳送的電子郵件也將在其中。 這就是為什麼我們建議使用IMAP的原因，除非您有特定的原因要使用POP3。

It’s also important to note that Microsoft usesMessaging API (MAPI) rather than IMAP for its email accounts. While they do differ, MAPI and IMAP both sync your emails between the client and email server.

還需要注意的是，Microsoft在其電子郵件帳戶中使用了Messaging API(MAPI)而不是IMAP。 儘管它們確實有所不同，但是MAPI和IMAP都在客戶端和電子郵件伺服器之間同步您的電子郵件。

POP，IMAP和PST和OST檔案 (POP, IMAP, and PST and OST Files)

If you have a POP account, Outlook stores all your emails and appointments in a Personal Storage Table(.pst) file. A PST file can be imported into Outlook. This makes it ideal for moving your email to a new computer or creating a backup you can save in case your computer crashes or becomes inoperable.

如果您有POP帳戶，則Outlook將所有電子郵件和約會儲存在個人儲存表(.pst)檔案中。 可以將PST檔案匯入Outlook。 這使得它非常適合將電子郵件移至新計算機或建立可以儲存的備份，以防計算機崩潰或無法使用。

Until Microsoft Outlook 2013, PST files were also used for IMAP or MAPI accounts. However, starting with Outlook 2016, the client stores all your emails and appointments from IMAP and MAPI accounts in an Offline Storage Table (.ost) file.

在Microsoft Outlook 2013之前，PST檔案還用於IMAP或MAPI帳戶。 但是，從Outlook 2016開始，客戶端會將來自IMAP和MAPI帳戶的所有電子郵件和約會儲存在離線儲存表(.ost)檔案中。

OST files automatically synchronize with the email server, as long as you have an internet connection. Unlike PST files, though, you can’t import an OST file into Outlook—because you don’t have to.

只要您具有Internet連線，OST檔案就會自動與電子郵件伺服器同步。 但是，與PST檔案不同，您不必將OST檔案匯入Outlook。

If you’re setting up Outlook on a new machine and connecting to your email account via IMAP or MAPI, all of your emails will be on the server, and they’ll download automatically.

如果您要在一臺新計算機上設定Outlook並通過IMAP或MAPI連線到您的電子郵件帳戶，則所有電子郵件都將在伺服器上，並且它們將自動下載。

The critical difference between PST and OST files is the contents of a PST are only available in that file. The contents of an OST, however, are also available on the email server and any other device you use to access your email account.

PST和OST檔案之間的關鍵區別在於PST的內容僅在該檔案中可用。 但是，OST的內容也可以在電子郵件伺服器和用於訪問電子郵件帳戶的任何其他裝置上找到。

您什麼時候需要它們？ (When Do You Need Them?)

Most of the time, you won’t have to worry about PST and OST files. You’re unlikely to see or directly access either unless you go looking for them.

大多數時候，您不必擔心PST和OST檔案。 除非您要尋找它們，否則您不太可能看到或直接訪問它們。

They’re really only important when you’re moving data to a new computer or want to archive your emails. If you use a POP3 email account, you’ll have to copy the PST file to your new computer, and then import it into Outlook, or you’ll lose all your emails.

僅當您將資料移至新計算機或要存檔電子郵件時，它們才真正重要。 如果您使用POP3電子郵件帳戶，則必須將PST檔案複製到新計算機上，然後將其匯入到Outlook中，否則您將丟失所有電子郵件。

If you use IMAP or MAPI, you only need to be aware of the size of your mailbox on the email server. If you ever reach the maximum size and want to keep all of your emails, you’ll have to export a chunk of them into a PST file, and then delete them from the email server.

如果使用IMAP或MAPI，則只需要知道電子郵件伺服器上郵箱的大小即可。 如果達到最大大小並希望保留所有電子郵件，則必須將其中的一部分匯出到PST檔案中，然後將其從電子郵件伺服器中刪除。

You’ll then still be able to view those emails if you import the PST file into Outlook, but they’ll no longer be on the email server.

如果您將PST檔案匯入Outlook，則仍然可以檢視那些電子郵件，但是它們將不再位於電子郵件伺服器上。

翻譯自: https://www.howtogeek.com/690076/whats-the-difference-between-outlooks-pst-and-ost-files/