WASHINGTON (AP)The Postal Service and major mailers appeared Friday to be close to an agreement that could lead to postage rate increases by the end of June instead of in the fall, a boon to the agency that faces billions in costs stemming from anthrax-by-mail letters. Under the proposed deal, rates would go up 8.7 percent on average, providing an estimated $6 billion in additional revenue for the post office, with the cost of a first-class stamp rising three cents to 37 cents. This is the same increase the Postal Service announced in filing a rate case last Sept. 11