Are deleted Mail messages actually gone or are they still stored somewhere?

You should assume that anything sent via email is still stored somewhere. Maybe in your Mac in a mail garbage can, in a cache, on your email providers storage, in the sender/receiver's email provider, on the sender/receiver's mail client somewhere, or with some government agency that is sucking up everything they can on the internet.

With Google IMAP, your mail may still be stored on Google's servers. You might want to login to gmail.com and check to see if something you deleted on your Mac has been removed when you look at it from the web interface.

Generally with gmail something deleted end up in the Trash folder and sits there for a month, then it is deleted, but it still might be residual copies on backups and other such places inside of Google (not to mention those government agencies).

As far as the question of taking up space, I have heard that what ever is emptied from trash (rather than 'secure empty trash') is stored and can be retrieved, but that it doesn't take up space as it is deleted if the system need more space. Have I got that right? And to the questioner point, is this also the case with the MacMail application?

allan299 wrote:

As far as the question of taking up space, I have heard that what ever is emptied from trash (rather than 'secure empty trash') is stored and can be retrieved, but that it doesn't take up space as it is deleted if the system need more space. Have I got that right? And to the questioner point, is this also the case with the MacMail application?

Close. A delete file just removes file system pointers to the data, but it does not erase the contents of the file.

Secure Erase does not work for an SSD, because of the way an SSD functions. Every write to an SSD actually allocates a new pre-cleared physical sector and the existing sector with your data on it will be moved to a garbage collection queue. Eventually sectors in the garbage collection queue will be pre-cleared and get used again. UNLESS the sector starts to fail, then it is retired, with whatever data was on it, and no longer used again.

A Secure Erase on a rotating hard disk will mostly erase the data, as long as none of the data sectors started to fail, and the disk controller didn't replace the sector with a spare, leaving some of your data in the replaced sector.

For both SSD and rotating hard disk, retired sectors can be read with the correct software.

If you are worried about anyone seeing anything on your storage under any conditions, the storage should have System Preferences -> Security -> FileVault enabled so that deleted files are just a random bunch of bits.

Thank you for the clarification. It is appreciated.