How to Make an HTML Signature in Apple Mail for Mountain Lion OS X 10.8

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There are plenty of tutorials online to create an HTML signature in Apple Mail with Snow Leopard, and you have probably already seen my tutorial on how to add HTML Signatures in Lion, but the process has completely changed for Mountain Lion. Here is how to do it:

  1. In, go to Preferences > Signatures and create a signature with any random content. Name it something meaningful. You will be swapping this out later.
  2. Write an html page inside of your favorite text editor. I use TextMate 2. The page should not have html,head or body tags, should include only inline css, and should only consist of basic html elements (div, span, img, a, etc...). Here is some example code to get you started.

    If you need additional help with html signature design or implementation, I have setup a small service called GiantUser (it's an anagram of signature) to do just that with very reasonable prices. Check it out!

  3. Open the folder
    ~/Library/Mobile Documents/com~apple~mail/Data/MailData/Signatures/
    to show your email signatures in Finder by holding down the Option key and clicking the "Go" menu in Finder. Check here for more tips if you are having trouble opening the ~/Library folder.
  4. When you created a temporary placeholder signature in step 1, Mail automatically created a ubiquitout_XXXXXXX.mailsignature file that represents it in this folder. Locate the .mailsignature file in the ~/Library folder. It will have a random name. If you need help, you can tap the spacebar when a file is selected and you can view the contents to make sure it is the right one. It helps to sort the folder by Date Modified
  5. When you have located the placeholder .mailsignature file, open it with your html editor. You will see a few metadata lines on the top of the file and some html code below it.
  6. Keep the top metadata lines, but replace the html in the file with your own from step 2.
  7. Save the file.
  8. This step is no longer needed thanks to a tip from gilliginsisland in the comments. We will keep it here for comparison, but please skip to step 9. Thanks! THIS IS THE MOST IMPORTANT STEP SO PAY ATTENTION. Even though you save this file, will use the original version and overwrite your new signature unless you lock the file. With your text editor now closed and the file saved, find it again in Finder and press command-i to bring up the info pane for the file. On this info pane, mark the "Locked" checkbox.
  9. Restart and go to Preferences > Signatures. If you have images in your signature, they will not show here in the preview, but they will show in the real signature if the image source location is valid.
  10. To test that it is working correctly, simply compose a new email and set the signature to be the one with the name you created in step 1. If the images show, and everything looks as it should, you have succeeded!

Finally, I run a small software company called Urban Apps. It pays the bills so I can take the time to write helpful posts like this one. If you found this page helpful at all, I would really appreciate it if you would check out my iPhone/iPad Apps on the iTunes App Store.

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