3rd Party Email Clients

Forgive me, but I posted this question to a different group, and I'm afraid the few answers I was given, habe left me even more perplexed.  Hope you don't mind if I try here, issue as follows.  Has anyone managed to solve the 3rd party email issue, as a result of virgin e-mail's security upgrade some weeks ago. Webmail works, I think I tested Outlook too, but I've been with Thunderbird for years. Would like to be able to continue doing so, but constantly been getting the password error (You know how frustrating it is if you've experienced it). The solution has something to do with Google App, but cant remember the rest of it. Tech support have absolutely no idea what I'm talking about, no surprise there, doesn't appear on their onscreen instructions obviously. Outside their remit, perhaps, in other words, not their fault. But there has to be a permanent fix, at least I hope there is?? Thank you group.