ROYAL Mail is expecting its busiest day of the festive season today as the final posting dates for Christmas approach. Scots are expected to post about 12.1m cards and letters today, double the amount posted on a normal business day. Scotland's Christmas mailbag is on its way to breaking the 200m mark for the first time. The last recommended UK posting dates are Friday, December 18, for second class mail and Tuesday, December 22, for first class letters and cards.