Outlook 2010 displaying inconsistent spacing between table cells

I'm designing an HTML Newsletter and I've run into this problem:

As you can see, the cellspacing is completely out of whack: there shouldn't (and CAN'T) be a spa开发者_如何学运维ce between the rows on the left and right column. I don't really know what the culprit could be, any ideas would be appreciated!

Here's the relevant source code:

<table width="740" cellpadding="0" cellspacing="0" border="1">
<tr>
    <td colspan="3">
        <img src="top.jpg" width="740" height="53">
    </td>
</tr>
<tr>
    <td colspan="3" height="200" valign="top" id="headerCell">
        <img src="header.jpg" width="740" height="200" alt="Headerbild">
    </td>
</tr>
<tr>
    <td>
        L
    </td>
    <td valign="top" width="600" bgcolor="#ffffff">
        CONTENT
    </td>
    <td>
        R
    </td>
</tr>

The HTML looks fine to me. Have you tried eliminating the unnecessary whitespace? That could be a possible cause (also, remember the great IE6, which had whitespace issues).

The HTML rendering engines in e-mail clients are just horrible. I've had to design some newsletters a while back and it sucked big time. Here's a nice collection of tips, maybe it'll be of some help.

I finally found out what was causing this spacing: a padding-top set on the center cell caused the left and right cells top edge to stay flush with the content-top of the center cell.