Looks like there may be a stolen mail problem in the neighborhood -- there's been some email traffic recently on the MPD 3D Substation listserve about it.
One person living at 13th and Irving St. NW reported seeing a woman take her mail. The victim then followed the woman, who then rummaged through some mail at another house on the 1100 block of Harvard St. NW, then went into another house on 11th Street. The victim tried to take photos of the woman, but they didn't turn out, and police came but the caller couldn't identify the woman for sure.
In response, a few other folks noted similar problems, on 11th and at 10th and Otis.
Aside from calling the police (which you should do) there's also the US Postal Inspection Service, which treats stolen mail very seriously. Their phone number is 410-715-7700. They also have an online reporting page.
Anybody else have this kind of problem?