THUNDERBIRD doesn't connect to server

yes, I saw that from the ATT help/support and its probably my fault ignoring the ATT email suggesting it 

What's had me puzzled over time is my wife's bellsouth address has continued to work on T-bird and, is not understanding why using  att/yahoo browser access works ok.

 adding to my befuddled dilemma is how/why  browser based gmail & android based phone apps can get the mail that t-bird doesn't 

Also adding is personal craziness of (after 25 years) giving up on wire line from the Bell System which rebates my monthly local service as a pension bene and my plan to go VoIP on Atl. BB....

and then disc'g Uverse www svc and just have ABB for everything  ..especially since T-Moblie wifi/hotspot/etc. gets the job done as BU to the world ......

Please forgive my personal mindgush as I wallow in the complexities wrought by the T1=1.544Mbps I was involved with debuting in '62........

At one time I was proud of the societal impact of telegraphy/telephony & all its derivatives 

Now its corrupted our very souls by too much faked fakery fakers creating alternate faked facts & alternative universes for the unsuspecting******

Bttom line, thanks for the prompt help ......if you've read this far my next ?'s relate to exporting t-bird mail files.....mailbird wants to import form t-bird servers......I want an app that takes mozbackup file & reads them outside of t--bird.......I dread the day when, maybe when I'm 101, I want to rant about something from a 2000 (Y2K) email.......LOL