Relocating Mail Off the Boot Drive

UPDATE 2018: MPG recommends NOT moving mail and similar things off the boot drive, due to maintainance headaches across sytem updates.

This is an advanced tip.

If you have moved your entire home directory, then there is no need to do this.

This trick lets you move your Mail folder out of your home directory onto your data volume. I’ve used this technique for years so that I can forget about having to back up my home directory (default location for Apple Mail) and simply back up my one data volume: Master. The same trick can be used for any similarly irritating program that insists on storing its data in your home directory, rather than giving you a choice (a few programs are too brain-dead for this to work). Programs like iTunes let you choose where to put your music; use that option.

Moving it

Your Apple Mail folder is in the Library folder of your home directory.

The trick requires starting Terminal. If that makes you uncomfortable, stop here! You are going to make a symbolic link.

0. Quit Apple Mail, and make a backup of your mail folder.
1. Copy the Mail folder to the top level of your data drive (or elsewhere, then modify step 3 appropriately).
2. Rename the original mail folder to Mail.old as an additional backup.
3. Start a Terminal window and type:

ln -s /Volumes/Master/Mail Library/Mail

This makes a symbolic link to the folder Mail on the volume Master (type the name of your volume, and use quotes around it if the volume name contains a space character). The resulting file Library/Mail is a tiny file that says “look over there on /Volumes/Master/Mail instead”.

From here on out Apple Mail won’t know the difference! Launch Apple Mail and verify that it worked. If you encounter problems, simply copy your backup back into place.

Confirm the change

Here, I’ve relocated mail to the volume Master:

diglloyd:Library lloyd$ ls -l
total 8
...
lrwxr-xr-x    1 lloyd  staff    20 Aug 29 12:47 Mail -> /Volumes/Master/Mail
...