While the easiest route is sending congratulations via the Kensington Palace social media accounts, there's also snail mail. (After all, Meghan recently shared that she does not look at Twitter. Plus, it's well known that the Duchess of Sussex, a former calligraphy instructor, is fond of putting pen to paper.)
THR Duke & Duchess of Sussex
The royal parents-to-be may live at Kensington Palace until their move to Windsor's Frogmore Cottage in the coming weeks, but their correspondence section is actually located at Clarence House, the official residence of Harry's father, Prince Charles, and Camilla, Duchess of Cornwall.
If you accidentally send a letter intended for Meghan and Harry to Kensington Palace, there's no need to stress—the mail will be re-routed to the correct place.
Although there are no guarantees, make sure to include your return address because you may receive some royal mail back!
Harry, 34, and Meghan, 37, have been known to thank fans who reached out following big events. Following their royal wedding in May, fans who offered their congratulations through the mail received notes cased in an envelope containing Kensington Palace's crest. The thank you cards featured the romantic black-and-white portrait of the couple taken on their wedding day by fashion photographer Alexi Lubomirski. The photographer also took the couple's dreamy engagement photos at Frogmore House in Windsor late last year.
The thoughtful notes also contain a sweet message written on behalf of the couple.
"The Duke and Duchess of Sussex have been overwhelmed by all the incredibly kind cards and letters they have received on the occasion of their Wedding and are so touched that you took the trouble to write as you did," the message read.
"It really was most thoughtful of you and greatly appreciated by The Royal Highness who send you their very best wishes," the message continued.
Meghan and Harry also thanked fans who wished them a happy birthday this year.
"The Duchess of Sussex is so touched you took the trouble to write as you did on the occasion of her 37th birthday," reads the back of the postcard, according to royal fan LoopyCrown3 on Instagram. "It really was most thoughtful of you and Her Royal Highness sends you her heartfelt thanks and best wishes."
For his 34th birthday in September, Harry chose to thank fans with a smiley photo of him from back in December 2016, when Harry visited to Camp Ayanganna, the headquarters of the Guyana Defence Force, in Guyana.
"The Duke of Sussex is most grateful to you for writing as you did on the occasion of his 34th birthday," reads the back of the postcard, according to LoopyCrown3. "It really was so thoughtful of you and His Royal Highness sends his warmest thanks and best wishes."