Actually, beg to differ on the inline — for email newsletters, that only adds to compatibility, in my opinion. Though, I tend to go a bit overboard sometimes and do stuff like this:
Text with a link to somewhere and stuff.
Although I second @Paulie_D’s comment that MailChimp (or other services) would be recommended, if you do have to use your own templates, don’t use background images: versions of Outlook don’t support that at all. So any table cell that needs a repeating image: avoid.
For images, stick with IMG tags, and for backgrounds, stick with just colors.