thunderbird is no longer supported.

Now receiving this message when "sending" emails: "An error occurred when sending mail. The mail server sent an incorrect greeting: Service not available." My ISP is Suddenlink. Generally the 3rd or 4th attempt at sending an identical email will go through...generally Also, sometimes it takes 15 to 20 seconds for a simple text email to be sent. I called suddenlink and they said they only support Outlook and suggested I switch to that. I may do so if Mozilla can't repair this issue.

They didn't say Thunderbird doesn't support suddenlink. It might be helpful to ask that support contact why THEY don't support Thunderbird (apparently their words), because with google search I'm not finding suddenlink's documentation that says Thunderbird is not supported.

My first contact with Suddenlink was by phone: "the only email we support is Outlook." My 2nd contact was by chat and they figured out the problem which happened to be on their end...not a problem with Thunderbird. What the problem was I don't know but they repaired it and all is working now. Thanks for your help...