Using Apple Mail to transfer Emails between Servers

You can use the Apple email client to transfer emails from one server to another using an IMAP email account added to the client. If you need to transfer emails from an old hosting server then this is one method you could use if your accounts were using the IMAP protocol

To prevent loss of emails when moving to a new hosting server, create an email forwarder on the old hosting server so that emails are sent to an active email account. You can use the Apple email client to transfer emails from your temporary account to the new server when it is ready. The forwarder should send the email to a service that is active and able to take your email content and attachment sizes. For example, you may want to use Google's Gmail which allows 25 MB attachment sizes. However, with the integration of Google Drive, then you can attach files as large as 10 GB. Make sure to add the forwarder before you transfer the domain.

This transfer method takes email from one IMAP account and then copies it to another IMAP account. You will have a source email account(on the old hosting server or another server), and a destination email account(be on the new hosting server). This may take some time if you are transferring multiple email accounts. Note that IMAP email accounts must exist before using the steps below.

Copying IMAP Email accounts using the Apple Mail client

1. 

   To start the transfer process, login to the Apple Mail client (version 9.3 is used in this tutorial). Make sure that you can see both the source and destination email accounts. The source will be your old hosted server or the email account where emails were forwarded. The destination will be your new hosting server location.
2. 

   On Apple computers copying files or other objects is typically done with a drag-and-drop action. You can do the same here or click on the folder or mailbox to select the emails that you want to copy over. You can select all emails by going to the menu and clicking on Edit, then clicking on Select All.
3. 

   Next, right-click with a mouse or CTRL-click (with a touch pad) and select Copy To from the pop-up menu.

4. Select the destination folder or mailbox. Once you have selected the destination, the files will immediately be copied over. Note that using the drag-and-drop option MOVES the email from one account to the another as opposed to copying it.

Please be aware that emails with with large attachments may require more time to complete the complete the transfer.