Good Morning

About a week ago the problem began. I could not use Thunderbird to send or receive mail.After numerous calls to my ISP I learned that they updated their server and changed the name. After considerable effort on my part, I was able to receive email but I still cannot send it from that app. Yesterday I again spoke to my ISP. They said that since I can use their website to send and receive email, I am on my own in respect to the app. I really prefer using the app. I tried changing the name in the outgoing server, but it did not help.
Any advice will be appreciated.