MailBox data shown more but .pst download less

I am taking the back up of email boxes (.pst ) file format , when I see it on outlook it shows for example 20-30 GB data in the mailboxes but when i download it as (.pst ) file. The size of .pst file is about 6-7-8 GB. Is the .pst file in compressed the mail box data, And  Is that file will  reflect all the data (mails) into the outook when i import it on other domain name .
Jawwad AzamSystem AnalystAsked:
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Andrew LeniartIT Consultant & Freelance JournalistCommented:
Is the .pst file in compressed the mail box data, And  Is that file will  reflect all the data (mails) into the outook when i import it on other domain name .

Yes, if mail is being saved in a PST file, then all data is saved in there. Are you sure you're not viewing an OST file?

Ie: You don't have an IMAP connection or are connected to an Exchange server or Office 365 Server? It's possible to have both depending on your configuration.

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Jawwad AzamSystem AnalystAuthor Commented:
Yes, I am sure its .PST only and  i have read .pst file is very sensitive. problem is the when I check in outlook (older account  on other domian) it asked click here to see older emails so there is a long list of email got after click . These email are not reflecting. Hope you understand my problem.
Andrew LeniartIT Consultant & Freelance JournalistCommented:
There must be something you're doing wrong with the export process. If the purpose is to back up the PST, simply take a copy of the entire PST and everything will be in the copy. To transfer that same data to an exchange account, import from the backed up PST into Outlook with an IMAP connection, or if using the PST on the other domain, simply connect the copied PST into Outlook. I'm not totally clear on what you're trying to do here?
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