Outlook can sometimes add a bit of spacing on the left and right side of a element that can cause some layout-related headaches. By using the vendor-specific mso-table-lspace and mso-table-rspace CSS properties, you can be rid of those spaces and continue on to tackle the million other problems caused by Outlook.
table{ mso-table-lspace:0pt; mso-table-rspace:0pt; }