Its really easy to solve in most cases, simply pop one of the following into the head section of your emailer html:
Method 1:
img {literal}{ line-height:0.1em; }{/literal}
Method 2:
img {literal}{ display:block; }{/literal}
If your dealing with web based email clients they typically strip out your head section, in which case go inline and add one of the above methods to the problem images style=”” tags