You can import mails from another client to your email hosting accounts. To do this you can use the import emails option from the OX webmail interface by following these steps.
Step 1: Log in to your webmail panel.
Log in to your webmail account using the username and password by visiting the webmail interface. You can access your mail by visiting webmail.yourdomainname.com
yourdomain.com represents the domain name for your email service.
Step 2: Navigate to Settings.
On the top right corner, click Settings.
Step 3: Import Emails.
On the settings page, click Advanced Settings (Beta).
Enter the email address and the password of the account where you want to import the emails from.
Enter the IMAP Hostname and the port number. You can get the IMAP hostname from the email hosting provider where you want to import the emails from.
Click Start Import to begin importing the emails.