Designing HTML e-mails is not like designing HTML websites. There’s a huge technology gap between e-mail clients and web browsers. It’s as if browsers keep evolving, but e-mail clients are stuck in 1998.
In the world of HTML e-mail, embedded and external styles are bad, CSS3 is bad, JavaScript is bad, while.. inline styles and tables for layout are good. In this world, old-school coding methods are alive and well.
It’s not surprising that Gmail will strip out CSS3 properties. Your best bet is to stick to tables and inline styles.
UPDATE: Gmail now supports embedded styles.
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