Hii, for conversion of Export office 365 to PST too, I suggest DRS tool. This tool has very useful features like you Can convert and recover Office 365 emails into PST and many different formats like DOCX, DOCM, MBOX, PDF, JSON, etc. also users can use CSV for email migration.
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Microsoft’s Solution to Export Office 365 mailbox to PST
Step1: Log in to Office 365 with Administrator credentials.
Step2: Open the Admin center and click on the Security option available on the left side.
Step3: Click on the Permission option and select the eDiscovery manager option.
Step4: Scroll down to the eDiscovery administrator option and click on the Edit option.
Step5: Now select the administrator for eDiscovery and click on the Save option.
Step6: After this, click on the search option from the left pane and then select the content Search option.
Step7: In the content search window, click on the new search option, provide the name and description for the new search, and select the location/mailboxes to export. At last, add conditions and click on the Submit button.
Step8: Now go back to the search window and select your last created search. Now a window pops up. Here click the Action option and then click Export result from the dropdown menu.
Step9: Once done, click on the Export option on the search window and choose your search (Search may take few hours to blink on the Export tab). Now copy the export key (will need in next step) and click on the Download results option.
Step10: After clicking on the download result option, a Microsoft Office client discovery utility will be downloaded on your system. Open the utility, paste the Export key in the respective edit box, and then browse the location to save the PST file. At last, click on the Start button.