Apple Mac OS X Mountain Lion 10.8 is now available. Once again, Apple updated with some changes. If you want to create a custom HTML email signature for Mail on Mountain Lion, the HTML coding part remains the same but the installation have changed. Follow this tutorial to create a HTML email signature file and to get it installed into the new version of Mail on Mountain Lion OS X 10.8.

For Mac OS X 10.7 users, please follow my previous tutorial: Create a HTML Signature in Apple Mail on Lion OS X 10.7.

Step 1: Designing the HTML/CSS


Before we begin, here are some basic but important notes to keep in mind as you design your signature. One major obstacle in designing HTML e-mail templates is that there are literally dozens of different e-mail clients out there (most if not all can’t handle CSS and HTML as well as our internet browsers can) so you have to keep your design and codes as simple and straight forward as possible.

  • Use tables for basic layout. The CSS float property is not supported in Gmail or Outlook, making CSS layouts impractical.
  • Use inline CSS. The style tag is not supported in Gmail, and support for CSS selectors is spotty.
  • Use only basic CSS properties. E-mail clients tend to be very picky about which CSS properties they support. Campaign Monitor has a great summary ofCSS support in e-mail to use for reference.
  • Use absolute URLs. Relative paths won’t work for an e-mail signature. So all your links need to be absolute URLs.
  • Link to images. I personally dislike e-mail signature images as attachments (it makes it easy to mistaken that image as a legitimate attachment). Because of this, I recommend linking to your images by placing them on a web server rather than including them as attachments.
  • Exclude HTML, HEAD, and BODY tags. When we get ready to save your HTML signature into Mail, make sure that only the relevant HTML is included in your document.

For my signature, I used a two-column table. I have my logo on the left and the text on the right. I placed each element inside its own SPAN division to have the text float left without it breaking off to its own line and so that I could use inline CSS to format each element. If you use a DIV instead of a SPAN, each element will start in a new line.

You can view my HTML design here and feel free to use it as a starting point for your own signature. Once you have the signature design opened, you may see the HTML codes by pressing down on Command+Option+U on Safari orCommand+U in Firefox. If you use another browser, find “View Source” somewhere under the browser navigation bar. Once you have created your HTML file, give it a name and save it to a directory that you will remember like on the Desktop. We will come back to this file later on.

IMPORTANT NOTE: In Safari 6.0, you will not be able to find the HTML codes by default. You have to go to Preferences>Advanced and check the box at the bottom where it says “Show Develop menu in menu bar.” Once this is done, you can find “Show Page Source” under its drop down menu or simply pressCommand+Option+U.

Step 2: Create Placeholder Signature in Mail

In, open Preferences and click on the Signatures tab. There you will see 3 columns, the 1st one are your mail box accounts, the 2nd one are your custom signatures and the 3rd column is the signature detail preview. Create a new placeholder signature by clicking on the plus icon at the bottom of the 2nd column and name it. Drag your new signature from column 2 into your preferred mail box in column 1. Select your preferred mail box in the first column and go down to Choose Signature at the bottom. In the drop down menu, find and select your new signature. Note: At this point you will not see your HTML signature design on the 3rd column yet. Leave the 3rd column as is for now. Close window and quit

Step 3: Open the Signatures Folder

On Finder’s top nav, drop down the Go menu and than hold down the Optionkey to see the hidden Library folder. Once the Library folder is open, go to: ~/Library/Mail/V2/MailData/Signatures/.

Step 4: Update Placeholder Signature

Find the signature that you just added (a file ending with a .mailsignatureextension). If there are multiple files in the folder, switch to list view. The signature that you just added in should be the file that was last modified a few minutes ago. When you have located the .mailsignature file, open it with your HTML editor (I use Coda but Text Edit would work just fine). You may see a few metadata lines on the top of the file and some HTML codes below it. Leave the top metadata info untouched, but replace the HTML (highlighted in picture below) with your own from Step 1. Hit Save and quit your text editor. Read the bottom of Step 1 to find out how to get to the HTML codes with Safari and Firefox.

Step 5: Lock Updated Signature File – Important Step!

This step must be followed correctly in order for this signature to work or else will use the original version of the signature instead of the new one. Locate the .mailsignature file that you just updated in Finder again. Press Command+I or right click on file to Get Info. In the Get Info window, mark the Locked check box.

***Another way to lock the file is by clicking on the gray text to the right of the file name on the header of TextEdit. A drop-down menu will pop up giving you the option to lock file. (See 2nd image in Step 4)***

Step 6: Check Installation

Testing out new email signature

Restart Your new custom signature should appear automatically when you click on Compose Mail. If not, make sure you have followed Step 2 correctly. Links will not work and the images if any may not show when composing an email. But the links will work and the images will show on the receiving end if the source locations are correct. Compose and send yourself a test email with your new signature selected. If the images show, the links working and everything looks as it should, then you have done this correctly. Good Job!

Summing Up

Feel free to contact me if you run into any problems creating your very own Apple Mail signature. I’ll be pleased to see your creative HTML email signature so please post your link in the comment area. Cheers!

If creating your own HTML signature seems a bit too much work or you just don’t have the time for it, please consider having me do it for you. For a small fee, I will design a few different options for you to choose from, write up the HTML codes, host your custom email images and help guide you through the installation process. Contact me for more info.

UPDATE 08-30-2012: Due to the high number of recent requests to create custom email signatures, I created a service section for signature design and development.