Another request for sample data.
As has been mentioned I would work backwards from the zip.
Once you have a zip I would query a zip database, store the results, and remove them & the zip from the string.
That will leave you with the address mess. MOST (All?) addresses will start with a number so find the first occurrence of a number in the remaining string and grab everything from it to the (new) end of the string. That will be your address. Anything to the left of that number is likely an addressee.
You should now have the City, State, & Zip stored in a table and possibly two strings, addressee and address. For the address, check for the existence of "Suite" or "Apt." etc. and split that into two values (address lines 1 & 2).
For the addressee I would punt and grab the last word of that string as the last name and put the rest into the first name field. If you don't want to do that, you'll need to check for salutation (Mr., Ms., Dr., etc.) at the start and make some assumptions based on the number of spaces as to how the name is made up.
I don't think there's any way you can parse with 100% accuracy.
