Click where it says "To:"

THANK YOU for that; I actually figured it out because I couldn't operate without copies and blind copies. Can I ask another? actually I have two more questions

What determines an email goes into the Important folder?? I wanted to use that folder for reference material, not all the emails that are going in there.

What is the difference between Junk and Spam? THANKS again Gardenerlola

Is this a Gmail account? They like to think they can tell what is important to you and set it up to work automatically. You can go to your Gmail account on its website and configure this and other behaviours. Thunderbird is just reporting things to you as it finds them; it doesn't itself create or manage such a folder. I'd think the "starred messages" feature is as close as it has, as a built-in feature, to mark significant messages, but you'd almost certainly have to configure Message Filters yourself to make it useful.

At one level, Junk and Spam are two words meaning the same thing. Another phrase you might see is "Unsolicited Commercial Email", usually abbreviated to UCE.

Practically, Junk is UCE that Thunderbird has identified using its internal filters. It needs to be trained to be useful. It learns by example what is Junk and what isn't, looking for trigger words in your messages. It usually just marks UCE as Junk, but can be set so that when you mark a message as Junk by hand, it will be automatically moved to the Junk folder. I don't know why it doesn't also move all the other, automatically labelled Junk messages. It will make mistakes, so it's important that you correct it, unmarking good messages and marking the bad ones it missed. J will unmark, j will mark.

Spam is almost always UCE identified by other software or systems. If you are using Gmail, they have a fairly good spam identifier that will whisk away anything it considers spam and put it into a separate folder. But do pay attention to what is put into this folder. Any security software you have might also try to identify UCE, and it will usually do this by inserting a label such as "[SPAM]" into the subject line.

That U for Unsolicited is the issue; if you have ever ticked a box or provided your email address then it isn't "unsolicited". In such cases if you ever decide it has become tiresome and you want to stop it, ask yourself if the sender is a reputable business, and if so, look for a way to unsubscribe. Otherwise, just delete it.

I get a fair amount of legitimate commercial email in my spam folder. I think folk sign up or register in order to access a website or create an account with an online store, and become bored of the resultant steam of newsletters and promotions, and start reporting it as Spam, and Google's spam system adds these messages or their senders to their spam blacklist. So I have to check my Spam folders, rescue the non-spam messages, and then I mark the residue as Junk, just to reinforce Thunderbird's Junk training. Because Gmail moves messages into the Spam folder before you download them, and Thunderbird's Junk Controls look only into your Inbox, Thunderbird doesn't get a chance to work on the messages in Spam.

You could set Thunderbird to deliver Junk messages to the Spam folder, if you think it's useful to gather it all in one place. For myself, the large number of false positives in my Spam folders means I need to keep the clutter down to a minimum to make it easier to spot the good messages in there.

Given that Junk is trained to MY needs, and Spam detection is influenced by millions of unthinking users who send anything they don't like to Spam, I'd probably do better to disable Google's Spam detection and allow Thunderbird to do it all. YMMV.