All About Hatching Eggs, and What to do With Them!
The hatch rates of shipped eggs are lower than of fresh, hand-delivered eggs, but you can hatch them successfully, and many, many people have!
First off, a few notes about the nature of shipping eggs and hatching shipped eggs. Eggs are heavy, fragile, perishable, heat-sensitive, and shock-sensitive. We pack our eggs very well, but have no control over how they are handled after they are handed over to the shipping facility. We also have no control over the weather, or storage conditions while they are in transit.
Having said that, we've shipped many, many shipments that were hatched successfully!
Some breeders will tell you things they "know" about what happens to shipped eggs, or why a hatch is or isn't successful, but the truth is that often we'll never know. However, there are some theories that are worth considering.
The first theory is that the yolk can get "stuck" in position from the egg not being rotated enough, causing the embryo to be locked in position, too. The theory is that as the egg is rotated, the yolk rotates within the egg, and is then the milieu it's exposed to is sort of refreshed - i.e., by rotating the yolk and putting the embryo in different parts of the white, it's never exposed to one location where the metabolites can build up and cause a stale or toxic environment for the embryo. This is the theory behind rotating the eggs during storage before incubation (to keep the yolks from getting stuck into one position) and during incubation (to keep the temperature within the egg uniform and to keep the embryo from getting stuck in a toxic pool of its own waste products). When the embryo rotates away from a "dirty" spot, the dirty spot can then diffuse the waste products out into the egg white over time, so that when the embryo is rotated back to or near that spot, it's now relatively less toxic.
The second theory is that micro-tears can result from shipping, particularly if the eggs have been pressurized aboard an aircraft, but also if they have experienced shear-forces from the box being roughly handled, or the eggs being packed inadequately for shocks. Micro-tears in the air membrane of the egg (that membrane that is so darned hard to get off if your hard boiled egg is too fresh, the membrane just inside the eggshell). Micro-tears could theoretically allow contamination, but the greater risk is that the air/water balance of the incubating egg is disturbed - i.e. that the egg loses moisture too quickly through the micro-tears when it's supposed to happen very slowly through the molecular pores in that membrane.
The third theory is that the jostling of eggs during shipment disorganizes the egg, sort of scrambles it. On a molecular level, the fertile egg is actually structurally organized, not just a random glob of white with a yolk plunked in the middle. There are distinct zones and molecular structures in place that guide embryonic development on a molecular level. The theory goes that a "scrambled" egg (not with the yolk broken, but just with too much shaking or shear force) has it's structure damaged or interrupted, such that the developing embryo loses its "blueprint" for development and at some point fails to progress. The disorganization may be by sheared structures in the egg, or by micro-bubbles or bubbles that have happened during handling.
All is not lost! Most shipped eggs can hatch!
When you get your hatching eggs, you can reduce the effects of the above by treating them as follows:
Picture from http://www.msstate.edu/dept/poultry/hatch.htm
Here are some links for you to study, about incubation and candling: