- Download and install Mozilla Thunderbird mail application on your mac device.
- During the installation process thunderbird will ask if you want to create a new account or sign in with an existing one. Select sign in with an existing account and when prompted sign in with the gmail account which you would like to transfer the mail to.
- Then go to “TOOLS” in the Thunderbird mail app and then select “ADD ONS” and search for the “IMPORTEXPORTTOOL” plugin and have it installed.
- Then go to Apple mail and click on the root folder where all is mail is stored and select export mailbox, this will ask for a location to export the mailbox, it is best to save it on the desktop or somewhere which is easily accessible. All you subfolders will be saved as individual .mbox file and they will have to be imported one at a time for example if you got 10 subfolders in your root folder there will be 10 .mbox files generated.
- Then go to thunderbird mail app and click on the importexport at the left bottom pane of the application and select import .mbox file.
- Then you will be asked to select a .mbox file, now got to the location where the exported mac mail was stored and select the .mobox file you want to start the process with.
- Once when done, the mail which is in that particular .mbox file will appear on right hand pane of the thunderbird mail app.
- On the left hand pane of the thunderbird mail app you will see the usual folder which you normally see in your mailbox, right click there and select create a new folder and give it the name of your root folder same as the one in your mac mail.
- Once done, click on the newly created root folder and select create a subfolder and give it a name of the .mbox file or a name you prefer and create a subfolder.
- Now click on the .mbox file you imported, when clicked the mail will show up again on the right hand pane.
- Highlight all the mail and select “move mail’, when clicked you will be asked for a location.
- Now select the subfolder which is in the root folder which you created in the thunderbird mail app and select ok.
- All the mail will be moved from the .mbox file to folder that you selected.
- When done delete the imported .mbox file and import a new one and then again create a new subfolder to move the imported mail data.
Once when mail has been moved to the created subfolder thunderbird mail app will synchronize the data with the gmail mail account and the newly created folders should appear in your web account and everywhere else you are signed in with your credentials.
Repeat the process from step 5 for all your mbox files.