Web hosting change - MX record settings did not transfer with domain

I transferred my domain from Network Solutions to Enom - during the transfer, there was an interruption in my mail service. I have done domain transfers before, but they were from Go daddy and I haven't ever had this problem with them. My question is that I had to reissue the MX records, I did that about 32 hours ago but I am still having issues with a couple of mail providers (yahoo for one). How long can DNS propagation take? I know the standard answer is 24 hours but if it goes past that time period and it still has not propagated, what can I do?