[POP3] Emails in the Kakao Mail mailbox are deleted when I open Outlook.
The "Leave a copy on the server" must be enabled in Outlook and other POP3 mail clients. Otherwise, due to default settings, a delete mail request is sent to POP3 when the mail client exports the email.

You can prevent emails from being deleted when it is exported from Kakao Mail to Outlook by following the easy steps provided in "How to save web mails" at the top of the page the has the shortcut to setting up the Outlook program. Click the Outlook program tab you are using for more information.

Use the following as reference if you are experiencing difficulties setting up the client program.

How to setup options to save POP3 mail originals
① Go to the Kakao Mail page > Click "Settings" > Click "IMAP/POP3 Settings" > Click "POP3 Settings"
② Go to "Save Original Message" and select "Save original in Kakao Mail", then click "Save".
※ POP3 settings can only be updated in Kakao Mail's PC version.