Follow these steps to easily import your data from other email clients into Apple Mail:
1. Open Apple Mail and go to File… then click on Import Mailboxes.
2. Choose the email program from which you're importing data, then click Continue.
3. Browse for the location of your email profile and click Choose.
4. Select the items you want to import and click Continue.
5. Click Done to complete the import process.
6. The newly imported items can be found in the Import folder
You have now successfully imported data from other email programs into Apple Mail!