Today is the United States Postal Service’s busiest mailing day of the year for cards, letters and packages. This is also the mail-by date for domestic standard shipping. The deadline for first-class and priority mail is Saturday, and the day before Christmas Eve is the last day take advantage of priority mail express. According to Kalona Postmaster Gae Walton, those planning to send mail to service members stationed outside of the United States should have it to the post office by Wednesday to qualify for priority mail express.