Samsung Captivate and Yahoo e-mail

Have the phone about 5 months, set up to get my e-mail direct to the phone. Not with an app just directly, all of a sudden not getting the email to the phone says my user name or password incorrect, have checked have the correct user name and password, how can i reset to get my mail again, do not like the droid app as it always freezes, prefer this way, any suggestions...Thanks in advance.