Thunderbird is compatible with most email providers if you have the correct server settings in your account settings. There have been several posts in the last couple of days about Verizon problems. So they are having problems or have changed their configuration and you need to conform to those changes.

I went to my verizon.net account to get the settings. Verizon was unable to bring up that information and said to try later. Since Verizon is unable to pull up my information, seems to me Verizon has a problem.