If you want to receive a letter from President Obama and his wife expressing congratulations to you on your big day, then all you have to do is send him a wedding invite. Address the envelope to:
Honorable Barack Obama and Mrs. Obama
The White House
Greetings Office Rm. 39
1600 Pennsylvania Ave.
Washington DC 20500
Although there is a very slim chance that the president will attend the wedding, you will at least, most likely, receive a letter of congratulations. It'll be a nice memento to keep in your wedding scrapbook or to frame up and display at home.
Source: Etsy user casalastudio