The Proton Mail Import-Export app(new window) is available to customers with a paid Proton Mail plan and allows you to export emails from your Proton Mail account or import emails from your other email accounts or from files stored locally on your device.
When you export emails, you have the option to download the files as EML or MBOX. The main difference is that the MBOX format exports each folder as a separate file, while EML exports each email as a separate file.
Most email clients, including Outlook, Thunderbird, and Apple Mail, support both EML and MBOX. You can also use some text editors, such as TextEdit, to open and view EML files.
If you want to export several messages from your account but not a whole folder or mailbox, we recommend exporting your files in the EML format.
If you want to export your mailbox or a whole folder, or you want to make a backup of your messages, you can export your files in MBOX format.
When you export emails, they are decrypted so that you can view them in other email clients or applications. When you import emails to Proton Mail, they are immediately encrypted with your PGP key.