Don’t worry that the seeds you ordered by mail will freeze when they are shipped, even if they travel in freezing temperatures. With the exception of a very small group of tropical plants with seeds that are never truly dormant (and whose seeds are rarely offered by seed companies anyway), seeds are totally indifferent to the cold as long as they are kept dry.
In various experiments, seeds were sent on trips of several months to over a year into space at temperatures close to absolute zero (?460° F/-273° C)… and they germinated normally after they were sown back on Earth!
Therefore, although you may freeze your little toesies getting out to the mailbox at subzero temperatures, the seeds it contains won’t be bothered in the least!
Thank you very much Larry, I was worried about the freezing temps. Now I can start ordering.