Address clensing and deduplication is a complicated process, particularly if you want to achieve the standard required for discounts on postage.

If you want a result that looks cheap and nasty, then find something that is cheap or free.

If you want the professional result needed to qualify for discounts then you need to buy professional address management software.

Each country has its own requirements for address formatting. In the UK, the Royal Mail site has links to some of the people able to deal with UK addresses. The mail authorities in other countries may have similar links.