I don't think that starting them inside is the problem. I start a lot of seed inside and rarely have problems with the seeds / seedlings rotting. If the seeds had sprouted in transport there is a good chance they could have started to rot already before you received them. That has happened to me too. I had two packs of seed this year that had sprouted in transport and both had already started rotting. I know that because the shoots were not a clean bright white, though they were intact. A slight yellow cast is all it takes and they are gone. Another problem could have been non sterile soil or over watering. Watering at night is also a common cause of rotting. I also had a problem with receiving rotting seeds that hadn't sprouted. I tried cleaning the remainder with hydrogen peroxide but they all rotted eventually. From articles I've read and people I've talked too, starting them outside directly in the ground also has it's problems.
