The 99-year-old conflict veteran, who raised £ 29 million for the NHS through the towers of his backyard, received a postmark.
Royal Mail will stamp all letters with the message to amuse Captain Tom Moore’s 100th birthday on Thursday.
All publications stamped until Friday must be marked “Happy 100th birthday, Captain Thomas Moore, hero of the NHS fundraiser on April 30, 2020.”
Royal Mail said it was “honored” to have had trouble applying the postmark.
World War II veteran Capt Tom of Marston Moretaine, Bedfordshire extended his problem to 200 laps after completing the first 100 laps 14 days ahead of schedule.
His preliminary fundraising goal of £ 1,000 was damaged in about 24 hours and he has now raised more than £ 29 million for the NHS.
David Gold, director of public affairs and coverage for the Royal Mail, said, “What Captain Thomas Moore has accomplished is truly phenomenal, and it is reflected in the affection shown to him around the world.
“As Royal Mail strives to maintain the bond between the nation throughout these difficult situations, we are honored to encounter difficulties with a particular postmark to celebrate its 100th anniversary.”
Royal Mail said it had to adapt its sorting machines in the South Midlands Mail Center to redirect all messages to Capt Tom in a dedicated collection box.
A spokesperson said staff have already processed more than 100,000 cards using the new process and expect thousands more before their birthday.
Volunteers were also brought in to open and display the thousands of cards, which are presented at the Bedford school where Capt Tom’s grandson is present.
On Friday, it was revealed that Capt Tom could be the main centenary to dominate the charts, after his duet with Michael Ball became number one.
Their You’ll Never Walk Alone cap bought 82,000 copies, the proceeds being donated to the NHS Charities Together fund.
Capt Tom also opened a brand new Nightingale Hospital in Harrogate on Tuesday.
He received a standing ovation from NHS and army personnel during the digital ceremony.