Archive for August 26, 2013

Monday, August 26, 2013

Showing Duplicate Messages in Apple Mail

Since Mac OS X 10.6, Apple Mail has hidden duplicate e-mails. It uses a loose definition of “duplicate,” which can consider two messages to be duplicates even if both their headers and body differ.

This has caused problems for me when dealing with mailing lists. For example, if a message is sent both to me and to the list, it’s hard to tell from what Mail shows whether I was sent a private reply or whether everyone on the list saw the message.

It can also cause problems when archiving e-mails or moving them between mail programs. Most people would expect the number of messages in a mailbox to stay constant. However, if you archive e-mails from Mail to EagleFiler, you may end up with what looks like too many messages in EagleFiler. And if you use Mail to import from EagleFiler, it may look like some of your messages were lost. In both cases, the right number of messages are there, but you can’t see that because Mail isn’t showing all of them.

Fortunately, there is a hidden preference to tell Mail not to hide the “duplicate” messages. You can just enter this command in Terminal:

defaults write AlwaysShowDuplicates -bool true

Apple also says that you can adjust Mail’s preferences so that when you click on a message it shows links to the duplicates. However, this does not seem to work reliably for me, and it’s only for individual messages. It won’t help you see how many messages are really in a mailbox.

Update (2020-01-25): On macOS 10.10 and later, the command is:

defaults write _AlwaysShowDuplicates -bool true

NSStatusItem Icon Sizes

Alastair Houghton (via Shane Stanley):

Unless I’m missing something, Apple has remained silent on this topic, and hasn’t provided any guidance at all. Further, the NSStatusBar’s -thickness method, which is supposed to return the height of the status bar, appears to always return 22. Which is a lie.


So, to fill this dearth of information, I thought I’d do some measurements. I’m using the Messages icon, the Time Machine icon, the Bluetooth icon and the Input Menu icon as my references for my measurements; these icons are all provided by the system and they’re all of a consistent size and alignment, so this seems to make sense.