I know this is the kind of question that gets asked all the time, but I have been through every answer I can find and nothing solves this. The problem is that outlook 2010 adds a one pixel gap under (or over) every image inside a table cell. (Whether it is below or above depends on whether you us valign="top" or valign="bottom"). Setting display: block; doesn't seem to help.
If you take a look at this example in Outlook 2010 on Windows 7 you will see a red line under the Google logo. Nothing I have done will remove this line.
<table width="275" height="95" border="0" cellpadding="0" cellspacing="0" style="border-collapse: collapse;" bgcolor="red">
<tr>
<td width="275" height="95" align="left" valign="bottom" style="font-size:0; line-height: 0; border-collapse: collapse;">
<img src="https://www.google.co.uk/images/srpr/logo3w.png" border="0" style="display: block; vertical-align: top;"></td>
</tr>
</table>
I am coming to the conclusion that is not possible to remove the line. Any one care to prove me wrong?