Cannot send email. message is "cannot send message using the server". re entered outgoing server info and connection dr. says it is connected but it still won't send. had this problem before and fixed by resetting up the whole account but lose all message

oops, first time on here and put all the info in the title. so i accidentally tried to send an email while at someone else's house. that screwed it all up. now i get the cannot send message using the server. i have re entered all the info into the outgoing server and saved. connection dr. seems fine with it all, but it still won't send. last time this happened, i reset my whole account but then lost all my emails. 😟 wondering if there is a different way to solve the problem. i am using Lion. thanks beth