As long as they are not too young, well packed and the weather temps are ok, I do not see why not but I have not mailed them. I just wanted to suggest that you also check in the Plant Exchange Forum (specially the posts titled "HAVE ,,, hydrangeas " or "WANT ... hydrangeas"). If unsure about the time, check to see if hydrangea mail order nurseries are making deliveries by mail.

I ordered some rose cuttings online last month and roses aren't as tender as hydrangeas. When I received them they were dried to a crisp and useless for propagating. It would be your best bet to look for already rooted cuttings. There are some Nikko blues and other varieties of rooted cuttings available for purchase on ebay. However I ordered a 1.5 gallon hydrangea plant a few weeks ago and when it arrived it was cooked from the heat. It had been in the 80's. They are very sensitive. The plant lost all of its foliage and is now beginning to leaf back out but it looked rough for a while and I was worried. I live in zone 6b.

Darren, I am willing to try a few. But need to know your growing zone - Sunset if possible so we know that if they do root, they will have a chance. I am in 8b, PNW.