Gmail does have a spam folder, if used. To mark mail as NOT spam, highlight message and click the 'create filter' option and mark as 'never send to spam'.

Thanks David Seems to have done the trick

I'd like to request a "not spam" button, which many other programs seem to have. The filter solution is all well and good, but doesn't account for new incoming mails that it's never seen before. So they'll still be marked.

Not exactly a reply but I am suddenly getting 100 spam emails a day, from home depot/samsung/and many other companies that I have business with but they are offers I did not solicit. I religiously mark them as junk (that is put them into the junk folder but Thunderbird does not seem to learn as I get them day after day.