The only way you can style the cells with a thin 1px line (or line different from the default) is via CSS though obviously you could link to an external CSS file rather than adding it to each cell via the style attribute.
Also in markup the TABLE border attribute only uses ‘pixel’ units in the thus your border=“0.6em” would be erroneous whereas border=“1” wouldn’t. As you can see CSS is the more flexible.
Unfortunately not, no. Email clients are fickle, you really need to specify the mark up on all elements. While most clients will propagate stuff like font names and sizes properly, the borders must be applied to each and every cell in your table.
It sucks, I know
You might be able to easy the suckiness of this situation a little by using shorthand, though:
Yeah, border=“1” should be putting it around all cells, not just around the table – unless you set something funky on the TD. As a rule of thumb IF you are going to use HTML in e-mails, (not that there’s a legitimate reason for legitimate e-mails to have HTML in them) you probably shouldn’t even be trying to use the STYLE attribute as it too is poorly supported.
BTW – you should probably be using TH instead of TD+B, try adding the SCOPE attribute, and remember that cells inherit width off of the first TR’s TD… News flash, there are more tags that go into tables than just TR and TD.