For a company that prides itself on appearances, making your emails look good on Apple's own Mail program is an absolute pain in arse.
I've tried lots of methods to try and get my lovingly made, HTML email signature to display correctly on outbound emails using Mail, and there never seemed to be an easy way that worked every time. Until I found this method.
Create your signature in HTML. It needs to be as basic as possible, with inline CSS and not too much extra coding. Some sites will say to avoid Dreamweaver, but you can use it, just make sure not to include any of the preformatted code above thetags. Also, make sure any images are hosted somewhere, so it can pull through the information when displayed in someone's email. Save the file somewhere where you'll remember it. Don't worry if you don't know how to make an HTML email signature, our essentials package can help with that (and a load of other stuff).
Open the Mail program, go to Preferences and the Signature tab. Highlight the email account you want to use in the first column, then press the + under the second column to add a new signature. Give it a name you'll remember, in this case My New Signature, and then move to the third column. It should add some text, but if there's nothing there then just type MY SIGNATURE. The important part here is to make sure the box under the third column that says "Always match me default message font" is NOT ticked.
Find the HTML file you made earlier and open it using CHROME – do not use the Safari browser as – Apple being Apple – it can make everything go a bit wonky. When you see your lovely signature on your Chrome browser, press ⌘ COMMAND + A to highlight everything, then ⌘ COMMAND + C to copy it all.
Head back to the Mail signature you were working on earlier. Click anywhere in the window on the third column, that shows the MY SIGNATURE text, then press ⌘ COMMAND + A to highlight it all, and delete it. Then press ⌘ COMMAND + V to paste in your new signature. You should see the new signature displayed, although the images will just be outline boxes – don't worry, that's normal.
Close this signature window down and go to compose a new email. Your new signature should now be displayed – including the images – in the email window, ready for you to send next time you want to email someone.
Isn't it beautiful?! I will add, I am standing on the shoulders of the giants of the Email Signature Rescue YouTube Channel. You can watch their explainer video here: