When you export your emails from Outlook, you create a backup of those emails on your computer. They are saved in a .pst file.
Exporting emails is helpful if you want to switch to a new email address and wish to retain the messages from your old email address or just want to keep a back of important emails.
Outlook lets you export your emails on both desktop and web. After exporting your emails, you can import the .pst file from an Outlook/Microsoft 365 email address or other email clients like Gmail and Yahoo.
Export an entire folder in Outlook desktop
From the Outlook desktop app, you can choose which folder to export. All of the messages in that folder will then be exported.
- Launch the app. Then, navigate to the File tab.
Select File. - Select Open & Export.
Click on Open & Export. - Choose Import/Export.
Click on Import/Export. - In the new dialog box, select Export to a file. Then, click Next.
Click on Export to a file. Then, click on Next. - Choose Outlook Data File (.pst) and click Next.
Click on Outlook Data File. Then, click on Next. - Choose the folder you wish to export. Then, hit Next.
Click on the folder of your choice. Then, click on Next. - Select Browse.
Click on Browse. - Choose where you want to save the exported file, then hit OK. Finally, select Finish.
Select the folder of your choice. Then, click on OK. 
Click on Finish. - (Optional) Enter a password for your file, then hit OK. You will see the file in the folder you’ve chosen earlier.
Click on OK. 
Check the folder to see the exported file.
Export your entire mailbox in Outlook Web
Instead of just a single folder, the Outlook web app can only export your entire mailbox. This is composed of all your messages, calendar items, and contacts.
- Sign in to outlook.com. Then, select the Settings gear icon on the top-right.
Click on the gear icon. - Click View all Outlook settings.
Click View all Outlook settings. - Go to the General tab.
Click on General. - Select Privacy and data.
Click on Privacy and data. - Click the Export mailbox button. The exporting process can take up to four days, depending on how many emails, calendar items, and contacts you have in your mailbox.
Click on Export mailbox. - After exporting is completed, check your Inbox for an email with the subject line “Your Requested Mailbox Export is Ready” Open the email and click on the link to automatically download the exported mailbox.
Open the email and click on the download link.
Export Specific Emails from Outlook
Unfortunately, there is no option for exporting specific emails in the Outlook web app. If you want to have an email as a file on your computer, you can do so by saving the email as a PDF.
On Outlook desktop, you can follow these steps:
There is no direct way to export a specific email from Outlook. But there is a workaround: copying the email to a new folder then exporting the folder. Follow these steps:
- Open the app. Then, right-click on the email you want to export.
Right-click on the email you need to export. - Select Move from the menu.
Click on Move. - Choose Copy to Folder.
Click on Copy to Folder. - Select the New button.
Click on New. - Enter a name for your new folder. Then, under “Select where to place the folder,” click on your email. Finally, hit OK.
Choose a name, click on your email address, then click OK. - Select your newly created folder from the list. Then, hit OK. You can now see your email in the new folder.
Click on your new folder. Then, click on OK. 
Click on the newly created folder to see your email. - To export the email, follow the steps for exporting an entire folder from the Outlook desktop app detailed above.