Can't say I agree with the chosen answer about adding width.
Your issue is the inline-block attribute. It's affecting all the user-agent defaults of the table child elements. Simply, replace display:inline-block with float:left and you get the same results with all the other css stlying falling into place. (text align e.g.)
.navInline {
float:left;
vertical-align:top;
text-align: center !important;
}
Here is a fiddle applying the new style.
http://jsfiddle.net/bdTUz/
BUT IMPORTANTLY... Your question states you are making an email template. Classes may not work. What I know from making html based emails, best practices are to add inline styles.
This link may be very helpful
http://htmlemailboilerplate.com/