This is "Such Great Heights" by The Postal Service:
I first heard of The Postal Service when I read that Owl City's music had been compared to theirs but I didn't hear any of their songs until I watched them perform on an episode of The Colbert Report a couple of years or so ago. The Postal Service have only ever released one album, Give Up, which they released in 2003 and re-released in 2013, the latter as a celebration of the ten-year anniversary of the album.
Sadly, after little activity in the aforementioned decade, The Postal Service announced in 2013 that they would be permanently splitting up, which I think is a shame. Their music is both interesting and imaginative, which is where the Owl City comparisons originate.