I am helping a friend clear up hard disk space. In order to find the biggest space takers, I used a filesystem exploration utility. To my surprise, I found that nearly 100 GB of the internal hard disk space was being used by mail attachments.

This is quite surprising as, as per Apple's philosophy of "automatic management" and I thought the Mail app could "intelligently manage" the attachments which were downloaded to the device. Through some digging in the Mail.app preferences, I found the "Download Attachments" option (which is per-account). Again, somewhat surprisingly, this is set to "All" by default. I set this to "None" so that attachments would only be downloaded when they were needed, which would most likely reduce the amount of disk space used.

However, there is the issue of dealing with the 100 GB of attachments already on the drive – changing the aforementioned setting does not remove attachments which have already been downloaded from the disk. Thus, I am tasked with the issue of removing these attachments in the safe way.

I want to remove these attachments preferably manually. I know there are third-party apps (such as CleanMyMac) which take care of email attachments, but I don't want to install a third-party app to do this.

One of the mail things I want to avoid is deleting the attachments from the mail server. Most of the articles found by Googling show how to delete attachments using Mail.app's "Message > Remove Attachments" menu bar option, which seemingly removes the attachment from the server, not just from the disk. This is not what I am after.

I found some useful information about how to go about doing this from this article: Go to ~/Library/Mail/V*/***/YourMailbox.mbox/B92.../Data/, search for all the folders named Attachments in this Data folder, and delete them – they will only be deleted from the disk and not from the server. I am hesitant to do this because I do not know if anything has changed with the latest macOS version(s) and whether this may have unaffected side effects.

As Apple seemingly does not have any articles explaining how to remove attachments from the internal disk (which seems like a huge oversight), is there a "proper," somewhat "cleaner" way to remove the attachments just from the disk?

  • Is this POP or IMAP? – Tetsujin Jun 8 '18 at 5:49
  • I'd advise against deleting files in folders that applications consider private, like with ~/Library/Mail, as it may have unintended consequences that get unnoticed until it is too late. You could instead remove your account from Mail and recreate it with that specific setting you mention to prevent attachments from being downloaded, that would kind of "rebuild" your mail database, but without attachments. – jaume Jun 8 '18 at 6:34
  • @jaume hmm… I tried removing the mail account in question and to my dismay it didn’t remove the mailbox from the drive… – Skeleton Bow Jun 9 '18 at 18:33
  • @Tetsujin IMAP (with Google) – Skeleton Bow Jun 9 '18 at 18:34
  • Ah, I'm not certain with IMAP, sorry. Wouldn't like to guess. – Tetsujin Jun 10 '18 at 5:38

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