If they're in LastName, FirstName order, it's quite simple: just select the
list and do Table | Sort.
If the last name is not the first word in the paragraph, then you can still
sort by Word 2 (or Word 3 if each includes a courtesy title), but you will
have to make sure that the last name is the second (or third) word in each
paragraph; you can do that by substituting nonbreaking spaces
(Ctrl+Shift+Space) for the spaces between extra words. For example, if you
have a mixture of John Jones, Mr. Bill Smith, Mary Jane Doe, etc., insert
nonbreaking spaces between Mr. and Bill, Mary and Jane, etc., then sort by
Word 2.
All of the above assumes that each address block is a single paragraph. If
the names and addresses have a paragraph break at the end of every line, you
have more work to do, but it's still simple provided you have an empty
paragraph between address blocks. If that's the case, Find and Replace ^p (a
paragraph break) with ^l (a line break--that's a lowercase L). Then replace
^l^l (two line breaks) with ^p, which will result in a separate paragraph
for each address block.
