Happy, well socialized puppies get along well with adult dogs as a general rule, but oftentimes, doorway excitement leads to aggression. The dogs don't mean to get upset, yet the circumstances and locations can predispose your pets to squabbles.
Part of that has to do with the close quarters of doorways, status of who gets to go first through the entry, and even a "mob mentality" can come into play. That's right, some kinds of aggression only happen in groups when the participants sort of egg each other on. It's comparable to a bunch of high-energy kids who are polite and well behaved citizens when alone--but in a group, the excitement can spill over into mob behavior that turns violent. You may have read about such instances with pet dogs that "pack" and attack livestock or even more tragically, turn teeth toward people.
This probably won't be a problem with very young pups, but the adolescent doggies and especially larger breeds have a greater risk for problems. Here's the latest article in my aggression series. Learn more about excitement aggression here.
Image © Amy Shojai, CABC