How to make a virtual view for all the incoming messages from several accounts, just like in Opera Mail?

Question

I want to have a replication of Opera mail feature. This feature enables you to aggregate all mail items from across all the e-mail accounts into a single virtual aggregated view.
That is, say, we have 3 different mail accounts. In Mozilla Thunderbird on a daily basis I check if there is something new in the incoming folder for those accs. To do that I click on the corresponding folder for every account. Now, what i want is to click on a single folder where I would have an aggregated virtual view of the incoming folder for all of those 3 accounts. I guess, same thing can be done with different kinds of mails, such as:
* Unread messages (after having viewed the mail item, it automatically goes straight into "Sent messages" aggregate view, listed below)
* Read messages
* Sent messages
* Spam messages
* Drafts, etc
Also there is this cool feature (virtual thing applies here as well) that helps to have a view of all the attachments across all accounts categorized into different descriptions, such as:
* docs (xls, doc, ppt, etc)
* images (jpg, png, etc)
* archives (zip, rar, etc)
More then that, it would still be better to have labling aggregation view feature across all acounts. That is, if we have marked important several messages in, say, 2 accounts, those should be seen in a single aggregated virtual view under name, say, "Important messages". Same can be said with flags, todos, etc.

Answer 1

Pop mail accounts can be set up to use a Global Inbox. Imap mail accounts cannot.
However, there are various 'views' in Thunderbird. I would suggest you try 'Unified'. This creates a visual Inbox containing all Inbox messages with sub folders showing individual Inboxes, so you can still see them separately if required.
via Menu Bar;
View > Folders > Unified
Via Menu icon
Menu Icon > Folders > Unified.
This view would show all the 'Important' tagged emails, so you could them sort by Tag.