Designing HTML emails on a Mac

I was recently approached by an IT recruitment company to come up with an idea for an HTML email that could also be used in other forms of online advertising, such as banners, MPUs and skyscrapers.
The result was the above which will be used as an HTML email and to be sent out to 20,000 potential customers.
Here’s how you do an HTML email on a Mac: Compose your email as a separate “index.html” document in a directory on your server. Don’t use much CSS (only for text formatting, don’t use divs) and put the CSS in the body not the head. Contain everything within a table where width="100%". And within that table put other ones with widths no larger than 600 pixels. Make sure all your image sources have full routes. Once you’re happy with the result, view the page in Safari and go File > Mail Contents of This Page (Command-I) and a beautiful HTML email will open up in Mac Mail for you to email the client.
The email should be welcoming and friendly with an eye-catching theme, enticing the recipient to click through to your client’s website.
Have a look at the other ideas I came up with for this HTML email brief.
I’ve been trying to design HTML emails in Mac for quite a while unsuccessfully.
This really saves me a lot of time and effort..
But, do you think there may be any version compatibility issues?
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