Consumers should save their money and send post second-class this Christmas for a slightly slower but more reliable service, according to a watchdog.
Consumer Focus said official figures showed that at Christmas only just over half of items sent first-class arrived the next day, but more than 90% of items sent second-class arrived within three days.
It claimed consumers could save £67 million sending Christmas greetings with a 32p second-class stamp instead of the first-class 41p option.
Royal Mail figures suggest 750 million Christmas cards will be posted this year.
Robert Hammond, head of post and digital communications at Consumer Focus, said: "Christmas is expensive, but if people make sure they don't get snowed under in the Christmas rush and post their Christmas mail in advance, they can save much-needed extra pounds.
"Especially at Christmas, everyone wants the things they post to get to loved ones in time and intact. So it's important to post early, wrap fragile gifts carefully and insure valuable ones. People should check letter sizes and the last posting dates, so friends and relatives aren't left disappointed if their presents don't arrive in time for the big day."
A Royal Mail spokesman said: "Customers should always use first-class for their mail to travel with priority as we sort the first from second class at the start of the sorting process, and that's the case at Christmas as at any other time as we always aim to deliver as much first class mail as possible the next working day after posting."