Post Offices all over the Central Coast are bracing themselves for the busiest day of the year today. Over 800-million pieces of mail are expected to enter the system nationally. Today’s high volume of mail is said to be a 40-percent increase in the average daily amount of about 559-million pieces of mail. Today is the recommended deadline for sending greeting cards and holiday letters to arrive in-time for Christmas, and tomorrow is the recommended deadline for sending packages using priority mail.